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Old 10-27-2019, 06:57 PM   #1
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Unhappy 98 Sunline Solarus Trailer, Furnace issue

I have a 98 Sunline trailer that all of a sudden the furnace will not start up.
I turn the thermostat up high, switch is on heat, but nothing happens. I expect the blower to start up and run for a minute or two then the heat to kick in, but I hear nothing and nothing is what happens.
I checked the furnace 12V fuse and it is good. This problem persist whether it is running on 12V or 110V.
When on 110V the fan will run if I switch the fan to "fan" rather than "auto".
Everything else, all lights, Stove, Refrigerator, all work fine. The furnace did work without 110V about 6 wks ago, but not now.



Anyone have any ideas what to check next please respond.
Also, I'm thinking of replacing the thermostat as I have noticed the caliberation is way off when I last used the furnace and I don't trust it. You had to turn the thermo up to about 75 to get it started when it was 60 in the trailer. It wouldn't start placed on 65 or so.
Do I have to buy some kind of special 12 volt thermostat or does any house type thermostat work. I'm thinking they are all low voltage, it that right?


Ralph Louks
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Old 10-28-2019, 09:58 AM   #2
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Hi Ralph,

The next time you are at the camper, take the outside grill cover off and get a pic of the furnace model number and post, or at least tell us the model number.

Something is not adding up on this statement.

Quote:
I checked the furnace 12V fuse and it is good. This problem persist whether it is running on 12V or 110V.

When on 110V the fan will run if I switch the fan to "fan" rather than "auto".
Everything else, all lights, Stove, Refrigerator, all work fine. The furnace did work without 110V about 6 wks ago, but not now.
The fan, if it is working on 110 volts, the fan should work on just the battery assuming the battery is good or at least supply enough power to run the fan. The entire furnace is 12 volts unless someone changed something. The 110 volts runs the power converter and the power converter creates 12 volts that then runs the furnace. If you are on just battery power, the fan should still run assuming the battery is good. Check and see.

Not knowing what T stat and furnace model you have, a simple home T stat "might work" or it might not.

Since you have a fan on and fan auto switch, your furnace must have more than 2 wires coming to it.

Take a pic of the T stat with the cover on it and then off of it. It is possible to just jump the right 2 wires together to fire up the furnace and test that the T stat is the issue. If the furnace runs all good with the correct 2 wires jumped, then you T stat is having issues.

Hope this helps.

John
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Old 10-29-2019, 07:56 AM   #3
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All the info needed for the furnace to do any thing comes from the T stat if there is no AC controls in the thermostat they will only be two wires they are low voltage' a simple test would be to twist the wires together. If it has 4 wires (AC) the red and black will be the ones. Some thermostats did have a small on off lever you might check and make sure that is not turned off. The thermostat is a pretty simple device it really is nothing more that an on off switch and are fairly bulletproof. So the key is no fan that has to be the first thing to happen. It is fused so that would be something to look at. The furnace is strictly 12 volts so it does not need anything other than a good 12 volt battery to make something happen.
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Old 11-04-2019, 08:45 PM   #4
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Okay Mainah and John, here's what I found out. At the bottom of this post should be photos of the thermostat and furnace motor.
First off after taking the cover off the thermostat I found it has 6 wires not 4. They are labeled as below:

label>> +7.5 Cool Fur Hi Fan Fan Gnd
color of wire>> Red Green White Blue Orange Blk

I did not find any on/off lever on the thermostat.
John, I jumped the right 2 wires as you suggested, but as you see it's the Fan and Ground, but it didn't do anything anyway. Also, jumping the Ground and Fur wires don't either. I have no idea what the post labeled 7.5V is?


I checked the 12V fuses, They are all good. The one marked Furnace is 25amp and looked good, I replaced it anyway, no change.

Here's the things I found. With the following settings:

Thermostat switch set to ON. Thermostat temp set to 90 degrees. Batteries charged to 12.3 V. Fan switch set on AUTO.

Results: Nothing happens, even after 5 minutes or so.
Voltage meter readings at corresponding wire screws:
Low fan .5V, High fan 11.3V, Furnace 3.0V, Cool 3.0V

Noted that the Fur and Cool readings of 3.0V seem to climb slowly, see next test below.

What is strange here is that even tho High fan has 11.3 V, the fan does not run.
( note: With this same setup and the generator running, both the low fan and high fan does run and the meter reading at the corresponding post is 12.3V for each) ( Also with generator running the Furnace and Cool posts read 7.5 V, but of course the furnace does not run) This at least tells me that the fan is good.


Thermostat switch set to ON. Thermostat temp set to 50 degrees. Batteries charged to 12.3 V. Fan switch set on AUTO.

Results: Nothing happens, even after 5 minutes or so.
Voltage meter readings at corresponding wire screws:
Low fan .5V, High fan 11.3V, Furnace 7.5V, Cool 7.5V

Of course I would't have expected the furnace to start here and the thermo setting is 50 degrees and the room is 65 degrees at this time, but just noting the meter readings.


I was about to switch to another house thermostat I had, but as you can see with the pictures I'm not sure it will work here. It is a Honeywell with places for 5 or 6 wires. They are labeled from left to right: G, W, Not used, Y, R, Rc. The model may be RTH630081005-0832 but not sure if that is the model number of something else. I have yet to find the install manual for that one that would tell me now the wiring would go.

One other thing, at about the same time that I noticed the furnace would no longer I was replacing my thermostat in my refrigerator. In the process of pulling the wires out of the fridge to the back opening, we not only pulled the old thermo wire out but also pulled the fridge light wire out also. Since I didn't care if I had it anyway (bulb burned out) we just taped up the 2 wires and left them in the back going nowhere but still plugged into the control panel.
Note however from my picture of the control panel that there is a blue wire coming out of the panel in the upper right corner that goes nowhere. It may have always been that way but I'm nervous that perhaps we accidentally pulled it out while working on the fridge problem.
Do you know if this control panel only services the fridge or does it also control the furnace????
If both, perhaps that wire to nowhere is the problem?

The furnace motor is Atwood Mobile Products, model 8525-111

Next are the photos I took starting with the existing thermostat:




Sorry, I don't know how to get the photos onto this forum. I have them on my phone and on ICloud but can't figure out how to imbed them in my message. Please advise.
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Old 11-04-2019, 09:27 PM   #5
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Quote:
Originally Posted by relouks View Post
Sorry, I don't know how to get the photos onto this forum. I have them on my phone and on ICloud but can't figure out how to imbed them in my message. Please advise.
First off, we need to see your pics. See here on how to either "attach" to a post OR how to "link" in pics from a online photo server that is made public viewing.

http://www.sunlineclub.com/forums/f1...html#post86041


This link will tell you how to upload pics to your personal album you can create. Then if needed you can link the pic from the album to post
http://www.sunlineclub.com/forums/f1...html#post87945

If you get stuck, ask away. Pics are so helpful in showing us what you are up against.

John
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Old 11-04-2019, 09:54 PM   #6
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It sounds like you have the Dometic heat and cool T stat.

Does it look like this?






If it is, this is the wiring diagram for it.


A few things,

The 7.5 volts is to run the T stat control circuits. It by itself does not control anything, it just powers the T stat control board.

The Fan, deals with the roof AC unit. As does high and low fan. The fan on the T stat has nothing to do with the furnace. The furnace and it's fan are self contained.

If that is your T stat, remove the cover, if you unhook the white FUR wire off the board and then jump from GND to the FUR wire, the furnace should run. The only reason I had you unhook the white wire is, I do not know if there is a back feed into the board if you just jump the terminals.

That jumper takes the T stat out of the system. If the furnace fan does not run after that, this comes down to either the Roof AC unit interlock is not working right or there is a issue at the furnace itself. The AC unit has an interlock so that you cannot run the AC unit and the Furnace at the same time.

Now is where pics come in handy of the furnace motor area with the cover off. The 8525-III I do believe has a timing relay on it to run the fan motor. But I am not 100% sure if later models of the 8525-III went to the fan control on the PC board. Seeing your pic would tell us immediately.

Once we know what your looks like, you can jump the right 2 wires at the furnace itself to simulate the T stat and that eliminates the roof AC unit interlock. The furnace fan is the first thing that turns on. If you have no fan, nothing else on the furnace is going to work.

The fan comes down to,

1. Is 12 volts live at the furnace?
2. Did the T stat signal make it to the furnace to turn on the fan?
3. If you have the T stat signal and no fan, then is power getting to the fan motor? This is where the timing relay comes in or the PC board if your board is newer and has the motor control on it.

Hope this helps

John
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Old 11-05-2019, 10:00 AM   #7
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Furnace issue


Yes John, that thermostat you showed with the photos is exactly what I have. I think I have the photos loaded now. Be sure to notice that stray blue wire on the control panel board I talked about.



I won't be up to my trailer until Saturday to try that wire test you wrote about.


Thanks so much for your help on this.


Ralph
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Old 11-05-2019, 10:20 AM   #8
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Hi Ralph,

Your pics are showing now. GREAT!

I will re-read your post with the pic and respond back later. The furnace you have is the vintage with the timing relay that runs the furnace fan motor.

To the blue wire at the fridge, I'll look up that PC board to figure out what is on that plug. That fridge looks like an RM-2652 model, by chance do you know if it is?

The only thing the fridge and the furnace share in common is the 12 VDC main supply and the 12 VDC negative. Normally they are on separate fused circuits. The furnace since it draws so much 12 volt DC power to run the blower, is normally on its own dedicated 15 amp fuse. The fridge, which also uses 12 Volts DC, is ganged with other 12 volt things on as the fridge does not really use a lot of 12 volt power.

Be back later

John
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Old 11-05-2019, 11:30 AM   #9
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Ok on heat demand you must have 12 volts + (to ground) at the red wire before anything happens. After about 20 sec. the fan should run if it does not fan relay, circuit breaker, broken red wire or bum motor. The fan is the key to the entire adventure once it runs all the other things get to play, air flow proofing, ignitor board, gas valve and the likes. They are dependent on the fan running. Not the other way around.
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Old 11-05-2019, 09:16 PM   #10
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Hi Ralph,

Something dawned on me as I was preparing a note for you, you said this

Quote:
Originally Posted by relouks View Post
I have a 98 Sunline trailer that all of a sudden the furnace will not start up.

I turn the thermostat up high, switch is on heat, but nothing happens. I expect the blower to start up and run for a minute or two then the heat to kick in, but I hear nothing and nothing is what happens.

I checked the furnace 12V fuse and it is good. This problem persist whether it is running on 12V or 110V.

When on 110V the fan will run if I switch the fan to "fan" rather than "auto".
Everything else, all lights, Stove, Refrigerator, all work fine. The furnace did work without 110V about 6 wks ago, but not now.
And then this,
Quote:
Originally Posted by relouks View Post
I did not find any on/off lever on the thermostat. John, I jumped the right 2 wires as you suggested, but as you see it's the Fan and Ground, but it didn't do anything anyway. Also, jumping the Ground and Fur wires don't either. I have no idea what the post labeled 7.5V is?

I checked the 12V fuses, They are all good. The one marked Furnace is 25amp and looked good, I replaced it anyway, no change.
As long as you have 12 VDC power to the camper, either on a charged battery or 120 VAC on a generator or plugged in, when you turn on the furnace on the T stat and the temp setting it high enough to turn on, with your T stat, you should hear a "click" in the roof AC unit. Even if the furnace did not start.

Assuming you heard nothing, no click from the AC unit when you turned on the T stat to furnace, that can be the issue, or at least one of them.

Lets get the basic understanding of what in the camper actually turns on the 12 VDC power to the furnace system. In your system, with that T stat, the T stat does "not" physically connect power to the furnace.

This T stat of yours,




Actually your Tstat only communicates to the roof AC unit control board. There is no wire connection between the T stat and the furnace. I know that may sound strange, but let me explain further as there is no wiring diagram anywhere that shows this.

The Dometic wall Tstat connects to the roof AC control board. On the AC control board is a relay which then connects to the furnace. When that relay is energized, it connects 2 wires from the furnace. One wire is 12 VDC power from the furnace, the other is 12 VDC power signal back to start the furnace. Then the furnace is up and going all by itself. This is part of the interlock I was talking about that you cannot run the furnace and the roof AC on at the same time as the AC unit controls are telling who runs when. Bottom line, if the roof AC unit control board is not working, the furnace will not turn on.

Let me show you in pics. These are from various campers I have worked on to create the right pics to show you. Yours may be slightly different but should not be by much.

Up above the AC ceiling mesh air filter inside is an analog control box. The analog control box looks like this.


Inside that box is a PC board, looks like this.


And the PC board out in the open, looks like this


If you look at the top left corner of the PC board, there is T3 and T4 and the words furnace. Two blue and white striped wires connect to T3 and T4. You can see them on the 2nd pic up too.

Here are those 2 wires hanging out of the box wire nutted to a 2 wire cable heading to the furnace. And not the T stat.


If you are into reading wiring diagrams, see here for the furnace connection.


On your camper, Sunline may have run 2 solid wires from the furnace to the AC control board as opposed to the 2 wire cable. I have seen them do different wiring types over the model years. If you follow those 2 wires down to the furnace, then wire nut onto a 4 wire pigtail plug at the side of the furnace. See here. This is a pic from a 2005 T2363 buried next to a cabinet. Your furnace connection plug may be buried next to some other wall. But your connection plug will be on side of the furnace that does "not" have the copper gas line going to it.


In this case see the 2 blue wires in the plug bundle. Those 2 blue wires splice into the 2 wire thermostat wire cable and run up to the AC unit to hook to T3 and T4 on the PC board. The bundle then plugs into the side of the furnace. The red is + 12 VDC power to the furnace and the yellow is - 12 VDC to the furnace. If you actually jump those 2 blue wires, it will fire up the furnace if all is working on the furnace.




That is how the furnace is wired to the roof AC unit and the AC unit is controlled by the T stat.

OK now the basics, when you turn on the T stat to furnace and it is set high enough to call for heat, did you hear a "click" (only 1 click) of the relay up in the AC unit? Yes/No? If there is no click, no run signal was ever sent to the furnace.

Check and see if you hear that relay click up above the air intake to the AC unit. If you do not have that, by jumpering GND and FUR (unhook white wire and jump to GND) at the T stat wires should turn that relay on. Assuming the AC unit has 12 VDC power. You really do not need 120 VAC to make that furnace relay turn on, only 12 VDC. This then rules in or out the T stat is working and the AC control board is working. If no Tstat action turns on the relay then the T stat may have issues. But jumpering should energize the relay if the board is working.

Now that you know to listen for the click, you can toggle the T stat furnace on and off a few times to make sure you hear it or not.

"IF" you heard the click, then the next reply will tell what to look for at the furnace.

Hope this helps

John
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Old 11-05-2019, 09:48 PM   #11
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Hi Ralph,

This assumes you now made it past the Tstat and the furnace relay click up in the roof AC unit. You have the click, but still no furnace action.

Now we start at the furnace. This will add to what mainah was saying in pics.

I took your pic and drew on it. This topic has some up before and we needed to show a pic explaining this, so it helps you and others.

The pic is "busy" but it will show what we are talking about. Again on "your" vintage 8525-III furnace. Atwood was changing things from the time yours was built up until 7/2001 when the main PC board runs the whole furnace.


Lets start with the basics. That 4 wire bundle connection plug brings in 12 VDC power and GND. And it has 2 blue wires heading to the roof AC unit relay.

Check on the main power circuit breaker between the incoming red (+ 12 VDC) and a yellow wire (- 12 VDC) that you get live 12 VDC power. The Tstat does not have to be on to get this voltage. No power, then figure out why the camper fuse circuit is not sending it.

Assuming you have power to the furnace, then we need to confirm the 12 VDC control signal from the AC unit made it back when the T stat calls for heat. On the circuit breaker is a blue wire. That blue wire is + 12 VDC that goes up to the AC relay. Make sure it has a good connection to send out power. The other blue wire comes back from the AC relay and goes to the fan motor timing relay. When the Tstat is on and the AC relay is on, does + 12 VDC end up at the furnace timing relay? That relay turns on the blower. If you have no power to the timing relay, then the blower motor will not run.

If you have power to the timing relay on the blue wire, then applied 12 VDC turns on a heater coil in the relay. In approx 20 seconds or less, the heat will trip a disk inside the relay and close the contacts to send + 12 VDC the blower motor by the red wire leaving the relay heading to the motor. If you have power to the heater coil on the blue wire and have no power to the red wire going to the motor, then the relay can be bad or the wire connections have issues. The timing relays have gone bad before.

At this point, until you can get the blower to run, nothing else is going to start on the furnace. Try and get you voltmeter on those wires at the plug in terminals to test.

You can jump the 2 blue wire coming from the AC unit to power up the timing relay if needed.

You can also just apply jump 12 VDC to the blower motor directly. Turn OFF the gas valve toggle switch so the gas valve does not open and OR unplug the cable connection from the ignition PC board. The yellow GND is already connected, just pull off the red blower wire from the timing relay and jump + 12 volts the motor direct to test if the blower runs.

Be careful of the heavy red ignition wire, it can bite like grabbing ahold of a spark plug wire, it is high voltage. If you get the motor jumped and running, the sail switch will make and will energize the ignition board if it is plugged in, then after a time period the burner ignition would start clicking. The gas valve switch is off so it will not lite teh burner and you do not want to run the furnace without the timing relay working, that is why I had to unplug the ignition board and or turn off the gas valve.

Hope this helps.

John
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Old 11-11-2019, 09:26 PM   #12
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Quote:
Originally Posted by JohnB View Post
Hi Ralph,

This assumes you now made it past the Tstat and the furnace relay click up in the roof AC unit. You have the click, but still no furnace action.

Now we start at the furnace. This will add to what mainah was saying in pics.

I took your pic and drew on it. This topic has some up before and we needed to show a pic explaining this, so it helps you and others.

The pic is "busy" but it will show what we are talking about. Again on "your" vintage 8525-III furnace. Atwood was changing things from the time yours was built up until 7/2001 when the main PC board runs the whole furnace.


Lets start with the basics. That 4 wire bundle connection plug brings in 12 VDC power and GND. And it has 2 blue wires heading to the roof AC unit relay.

Check on the main power circuit breaker between the incoming red (+ 12 VDC) and a yellow wire (- 12 VDC) that you get live 12 VDC power. The Tstat does not have to be on to get this voltage. No power, then figure out why the camper fuse circuit is not sending it.

Assuming you have power to the furnace, then we need to confirm the 12 VDC control signal from the AC unit made it back when the T stat calls for heat. On the circuit breaker is a blue wire. That blue wire is + 12 VDC that goes up to the AC relay. Make sure it has a good connection to send out power. The other blue wire comes back from the AC relay and goes to the fan motor timing relay. When the Tstat is on and the AC relay is on, does + 12 VDC end up at the furnace timing relay? That relay turns on the blower. If you have no power to the timing relay, then the blower motor will not run.

If you have power to the timing relay on the blue wire, then applied 12 VDC turns on a heater coil in the relay. In approx 20 seconds or less, the heat will trip a disk inside the relay and close the contacts to send + 12 VDC the blower motor by the red wire leaving the relay heading to the motor. If you have power to the heater coil on the blue wire and have no power to the red wire going to the motor, then the relay can be bad or the wire connections have issues. The timing relays have gone bad before.

At this point, until you can get the blower to run, nothing else is going to start on the furnace. Try and get you voltmeter on those wires at the plug in terminals to test.

You can jump the 2 blue wire coming from the AC unit to power up the timing relay if needed.

You can also just apply jump 12 VDC to the blower motor directly. Turn OFF the gas valve toggle switch so the gas valve does not open and OR unplug the cable connection from the ignition PC board. The yellow GND is already connected, just pull off the red blower wire from the timing relay and jump + 12 volts the motor direct to test if the blower runs.

Be careful of the heavy red ignition wire, it can bite like grabbing ahold of a spark plug wire, it is high voltage. If you get the motor jumped and running, the sail switch will make and will energize the ignition board if it is plugged in, then after a time period the burner ignition would start clicking. The gas valve switch is off so it will not lite teh burner and you do not want to run the furnace without the timing relay working, that is why I had to unplug the ignition board and or turn off the gas valve.

Hope this helps.

John
John, I was up to my property in Northern Michigan last Fri & Sat. My main work was in getting my rig winterized and do a little deer hunting. I did get several hours to work on this problem. I will not take the time and effort to try to upload any pictures to this message because the pics you have in this thread are about the same as what I have anyway. The photo you have of the furnace/motor is exactly same as mine. The wires are even twisted around almost exactly as mine.
A few things I found out however or am concerned about I do not have electric service at my property, so everything runs on solar power charged batteries or if need be a generator. I have had a difficult time for the past 6 weeks or so keeping my batteries charged. We have not had much sun for the solar, and it is not nearly as strong this time of year, plus the temperature being cold (20 to 30 degrees last weekend) doesn't help batteries to hold a charge.
So I ran the generator a couple hours and got the trailer batteries (I have 2 of them coupled together) charged to 13.7V. I started checking some of the things you mentioned.

( with running only on battery power)

1. I removed and twisted together the blk gnd wire and the white fur wire on the Dometic Tstat. (With system switch set to furnace) Nothing happened.

2. Returning the wires back to normal, I did get a click from the roof fan area when I moved the Tstat upwards to about 80 degrees. Click on the way up and down.
3. Next I started the generator and tried the same thing as the above step, but moving the tstat upwards to 80 degrees caused the roof fan to start up. Move it below 80 and the fan would shut off. I don't understand why that noisy roof fan would start up when I had it set on furnace and called for heat. I think normal is for the furnace fan to start up, not that roof fan which I thought was only for cooling? If I let it run, after 5 or 6 minutes it will shut off?

4. Okay, back to battery power again, I took the roof fan area apart, took off the cover, the filter, the metal plate on the box, but it was just a mess of wires to me so didn't do anything else it that area.


( I was unable to see pictures you put in the forum and the notations you put on them because I was unable to get Internet there in or around the trailer. Also, the email that gets sent when you reply only has a liink to staticflickr.com which I cannot bring up while at the property either. I did do a print of the email before I went up there so I did have the comments you put before the pictures and the link, but no pics. I am going back there again this coming weekend, so I have printed out the pics on my home desktop and will take those with me.)


5. Going the the picture you sent of the furnace area on the outside. Under battery power I checked for voltage where I could without pulling any plugs apart. On your pic where you have labeled the wires, on the second arrow where you have the red circle, I have that blue and red wire going into a plug. With the system set on furnace, both the blue and red wire had 12.7V at the time. moving Tstat control higher of lower didn't change anything. Generator was running. Without generator, voltage on the two wires is only 11 to 12v at the time of testing.



6. Also, checked the exposed connector for the furnace blower motor timing relay. The top of the relay had 11V, the bottom had none.


7. I did notice that my batteries drain fast in the cold up there, so after a couple hours I do not get good voltage and wonder if that could be a problem. With the generator running, the Furnace wire by the fuse panel will have 13V, but the fur wire in the Tstat will only have 11.4 to 11.8. Is it possible that is not enough to kick in the furnace?
8. Yes, the fridge is model RM-2652. I'm still curious about that blue wire hanging there. I am not sure of the timing, and am not sure that the last time the furnace was working was before I changed the tstat on the fridge or just after. The fridge tstat was changed around Sept 10th.



So I'm going back Friday and can do some more testing armed with the photos now, but any other help you can give me is welcome.
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Old 11-13-2019, 11:57 PM   #13
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Quote:
Originally Posted by relouks View Post
The photo you have of the furnace/motor is exactly same as mine. The wires are even twisted around almost exactly as mine.
Just FYI, I took your pic and drew on it. It is your furnace.

Quote:
Originally Posted by relouks View Post
So I ran the generator a couple hours and got the trailer batteries (I have 2 of them coupled together) charged to 13.7V. I started checking some of the things you mentioned.

( with running only on battery power)

1. I removed and twisted together the blk gnd wire and the white fur wire on the Dometic Tstat. (With system switch set to furnace) Nothing happened.

2. Returning the wires back to normal, I did get a click from the roof fan area when I moved the Tstat upwards to about 80 degrees. Click on the way up and down.

3. Next I started the generator and tried the same thing as the above step, but moving the tstat upwards to 80 degrees caused the roof fan to start up. Move it below 80 and the fan would shut off. I don't understand why that noisy roof fan would start up when I had it set on furnace and called for heat. I think normal is for the furnace fan to start up, not that roof fan which I thought was only for cooling? If I let it run, after 5 or 6 minutes it will shut off?
As fyi, this is the wiring diagram for your Tstat


Something is not adding up on your Tstat and or the roof AC unit control board. As long as you are sure the T stat was set to heat, the fan should not turn on. The AC roof board may be having issues and that is what is not turning the furnace on.

At this point, I would suggest you to jump around the roof AC unit T stat and control board and turn the furnace on by jumping it on. I’ll explain below. There will be no T stat in control, but you can then confirm the furnace works or not. There will be no harm to the furnace to jump the T stat connection circuit, it will just keep running until you un jump it and it’s timer cools down to shut it off. Just do not leave it jumped on and leave the camper as it will not shut off. We can came back to the AC unit/ T stat issues once you know the furnace works and you have some heat.


Quote:
Originally Posted by relouks View Post
5. Going the the picture you sent of the furnace area on the outside. Under battery power I checked for voltage where I could without pulling any plugs apart. On your pic where you have labeled the wires, on the second arrow where you have the red circle, I have that blue and red wire going into a plug. With the system set on furnace, both the blue and red wire had 12.7V at the time. moving Tstat control higher of lower didn't change anything. Generator was running. Without generator, voltage on the two wires is only 11 to 12v at the time of testing.
The good news, you have 12 volts as incoming power to the furnace with the genny running. For now, stay on the generator until you at least know the furnace runs and works. Low voltage at the furnace can make the blower run too slow and it will not fire the burner.

Here is the pic for easy viewing,


Quote:
Originally Posted by relouks View Post
6. Also, checked the exposed connector for the furnace blower motor timing relay. The top of the relay had 11V, the bottom had none.
I’m assuming you mean you have 11 volts on the red wire at the top and 0 on the red wire on the bottom of the timing relay. Part of this points to that the Tstat and the roof AC unit may not be sending a run signal to turn on the timing relay.

Quote:
Originally Posted by relouks View Post
7. I did notice that my batteries drain fast in the cold up there, so after a couple hours I do not get good voltage and wonder if that could be a problem. With the generator running, the Furnace wire by the fuse panel will have 13V, but the fur wire in the Tstat will only have 11.4 to 11.8. Is it possible that is not enough to kick in the furnace?
The Tstat wiring is not really a true 12 volt circuit. It is more like a 7.5 to 8 volt setup. The T stat voltage measurements are not part of the issue as they are not directly from the main camper 12 volt system. I do not want to confuse you on this, the T stat communicates “only” with roof AC unit control board directly. The AC control board uses a relay on the board, to turn the furnace on and off., not the T stat. The AC PC board sends down to the T stat 7.5 VDC it created on the PC board to run the T stat. The T state sends signals to be on or run signals back to the PC board in what we call a “sinking” signal. Sinking in electronic terms means, the signal that came back to the PC board was not a positive voltage signal of 7 to 12 volts, it was at DC (-) (DC gnd) negative potential. The T stat wire signal to the PC board floats high with a positive voltage when no signal is sent. Then the T stat sinks the voltage to 0 volts to DC – potential (DC gnd) and that sends a signal to be on or run signal back to the PC board. The PC board is looking for a DC – (gnd) signal to know to turn on. This works backwards of a sourcing signal you are used to which is, you put positive power on something it turns on. A sinking signal needs to be a DC - (gnd) potential to be on.

The first thing to do is jump the furnace run signal to be on. This will mimic the T stat telling it to run. There are 3 places you can jump the furnace to run. The question will be, which one can I actually get to fairly easy. You pic which one works best for you.

1. At the roof AC control box area, behind the mesh filter is a bundle of wires. This bundle hanging out in my pic


You are looking for the 2 wires that come out of the control box that are blue with a white strip. They are wire nutting in this pic to a 2 wire thermostat cable with a red and a white in a brown insulation sleeve. One of those brown or red wires is + 12 volt power from the furnace. It is the blue wire you measured at the furnace that had 12 volts on it. The other wire, goes back to the furnace to turn on the timing relay, the run signal. Undo the 2 wire nuts, and twist the brown and white thermostat wires together and put a wire nut on it. The 2 blue striped ones, you can tape off for now as they are not use in the jump setup. If the 12 volt power is on from the battery or genny running, be careful not to touch the wires to the metal case or you will blow the fuse in the camper fuse box or trip the furnace circuit breaker. The furnace now has a run signal. And there is no connection to the Tsat anymore.

2. The second way is to fund this bundle of wires at the back side of the furnace. This is the other side of the white/clear plastic plug coming through the furnace.


The 2 blue wires in that bundle from the furnace connect to the other end of the thermostat cable that we just talked about in option 1 up in the AC unit area. Instead of jumping the 2 wires up in the AC unit area, you undo the wire nuts here on the 2 blue wires and jump the the 2 blue wires here to send a run signal to the furnace. You can tape off the 2 thermostat wires. Again be careful not to touch the blue wire to the side of the furnace or you will trip the fuse or circuit breaker. One of them is +12 VDC. I have no idea on your floor plan if you can even reach this wire bundle short of pulling the furnace out.

3 The third way is to jump the run signal right on the timing relay. Looking at the timing relay there is a blue wire on the left side that came from the roof AC unit all the way down to the relay. That terminal on the blue wire of the timing relay needs to be jumped hot with 12 volts which mimics the T stat calling for heat. Which when the relay is energized, it times a few seconds then turns the blower on and sends power to the sail switch inside the motor. Here you have to jump with an alligator clip jumper or some test wire from the red incoming 12 volts + hot line to the terminal on the relay under the blue push on connection. The blue wire has to remain on the terminal as it feeds the sail switch power.

One of those 3 options you will pic and will send the run signal to the furnace to start up. After a few seconds of jumping power to the relay, the blower should start, then a short while later, the ignition system will start sparking and the gas valve will open. And if the gas is on, it will try and light. This all starts with the blower running and the blower has to run fast enough to turn on the sail switch which senses enough air moving by the fan. Low DC voltage will not allow the fan to run fast enough and the burner never to start.


Quote:
Originally Posted by relouks View Post
8. Yes, the fridge is model RM-2652. I'm still curious about that blue wire hanging there. I am not sure of the timing, and am not sure that the last time the furnace was working was before I changed the tstat on the fridge or just after. The fridge tstat was changed around Sept 10th.
The fridge is not connected to the roof AC unit or the furnace. The only thing they have in common is the same 12 volt battery + and -, but there is no control interlocks. I’ll have to look up the blue wire.

Here is the service manual on your furnace. It has all Hydro flame furnace in it. You only need the 85/ 8500 series info Sunline Coach Owner's Club - Sunline Owner's Files - Atwood 2003 Furnace Service Manual

Page 10 on the lower right corner under “85-III Local Sense” is the wiring diagram on your furnace.

Page 16 tells the sequence of operation.

Page 23 to 35 tells more info on the furnace.

This could be as easy as just jumping the run signal to the furnace and it takes off and works. Then all you have to do is deal with the T stat situation.

OR you can’t get the blower to run, problem 1, Or the blower runs but it does not work the ignitor or gas valve. Or the burner electrodes have issues inside the furnace or something else.

Good luck and hope this helps

John
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Old 11-14-2019, 08:49 PM   #14
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Something I had forgot to mention on your battery going dead so fast in case you didn't know, do you disconnect the battery when you leave?

There are small devices that use power all the time in the camper. The LP gas detector and the radio light display have no on/off switch. They are on whenever the battery is connected.

Many times the roof antenna booster gets left on, and on some RM2652 fridges have a climate control heat strip on the door gasket to prevent condensation and freezing the door shut. Some folks do not even know it exists to know to turn it off. If that is left on, even with the fridge off, it will pull an amount of power from the battery.

With these things on in a camper and no shore power on, they can drain a battery down in a week or less if all of them are left on. Being in the cold makes it even worse.

If you have a battery disconnect switch, turn the battery off. If you do not have one, unhook the negative wire off the battery. You can leave the positive on. Reason for pulling the negative is, it is safer to unhook it as if your tool touches the siding on the negative in the process, you to not create a dead short on the battery and sparks will fly. Your tool can still cross by accident to the positive post so be carefull, but unhooking the negative adds a level of safety better then taking off the positive.

To help save the life of your battery, since it has been drained down many times now. And, odds are high you did not run the generator long enough to ever get the battery back to 100% charged. It can take a day to 2 non stop charging with a 10 amp charger to get a battery back to 100%. Suggest bringing it home and charging it up to 100% on a charger. If the battery goes dead on you out in the cold, if it gets cold enough, it can freeze the battery and total battery death soon follows. This does not happened when the battery is charged, but can when it is dead.

Hope this helps

John
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Old 11-16-2019, 02:20 PM   #15
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John, thanks for the three test I could do. So I decided to try option three first since it seems to be the simplest. I did what you said I had a lot of trouble with that roof fan return getting a connection there, but finally did and the blower started up after a few seconds followed by the furnace burner a bit later. Great news as I think that means the blower itself and the burner are OK.

Next I tried option one. Located the blue and white striped wires that went into the metal panel marked furnace. I followed those outside to twist nuts, I had a blue and red wire on one, and a blue and white wire on the other. The only brown was in the mess of wires and it was just sitting there going nowhere, not taped or anything, looks like not used. Twisted the red and the white wires as you said and the blower on the furnace started up followed a minute later by the furnace burner, same as in the other option.

I didnít try the second option as I didnít think it was necessary, and wasnít finding those wire bundles anyway.

So what do these test Tell is John? Youíre probably saying it looks like that relay is not working maybe, let me know what you think. I am still up by the camper until Sunday afternoon, so still would be able to try something tomorrow afternoon if needed

Ralph
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Old 11-16-2019, 04:11 PM   #16
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Hi Ralph,

Wow, you did good!

By chance did you turn the LP gas on and did the furnace fire off when you jumped the wires? You can test that if you didn't, from what you are reporting the furnace itself is operating the way it is supposed to once it gets a run signal. And you can let it run for a good while too. It will automatically cycle the burner on and off when the heat chamber gets to the high limit. Then when it cools a bit, the burner will come back on and it will keep doing this. The blower is running all the time when this is going on.

You are the T stat in this case, jumping and jumping the wires to get the furnace to run and stop. And once you jump it to get running, when you jump it it, the burner will shut down if if is not already but the blower will run for a few minutes to cool the system down and then it will shut itself off.

The only caution is on jumping the wires is, when you leave the camper there is no T stat and it will run non stop for hours which is not good.

You really did not have to try to jump the furnace on all 3 different ways. You only needed to do one of them that you could get to the easiest. So no need to think about trying option 2.

BUT, buy you jumping the furnace doing option 3, meaning jumping it at the furnace itself on the relay, and did I get it right, the AC fan came on then?

Was the T stat inside even turned on? Trying to understand this as the fan is not tied to the furnace relay unless something is wired wrong. BUT, if the T stat inside was on, and then the fan started running, that is an issue with the AC unit, not the furnace. Need to understand this better as nothing you did on the furnace jumping should of turned then AC fan on. But the T stat and AC control board could have issues.

And now that your furnace does run, or seems to be, the AC unit control board and or the T stat has issues. Now comes, what do you want to do right now? Fix the AC unit, or do a temporary install of a new T stat to just run the furnace and deal with the AC later? They sell $20 - $25 battery operated T stats that will run the furnace. They are dry contact ones used to turn on a furnace or a AC unit. And later it can be used to run the AC unit too, But your control board may have issues. You may have to order a new control board.

Question, do you know if the AC compressor turns on or just the fan when this phantom fan issue is happening? You can tell by the sound of the AC when the compressor is on, but you have to know what to listen for. Unless you have an AC clamp on amp probe, we can tell that way too by the total AC AMP draw.

Make sure you take pics of the part number of the AC control box and the Roof AC unit so we can look up parts during the week.

Good luck

John
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Old 11-17-2019, 06:52 AM   #17
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John, in answer to a couple of your questions, yes the furnace burner did come on on both of those test, heat was coming out inside the camper.
And the option three test I had the generator running the whole time. In the option one test I didn’t have it running the furnace did start up heat was coming out, but the battery was getting too low and as you said before the fan started going slower and slower, so I started the generator and then went back to normal speed.
In both test I believe the furnace continued to run even if I turn the furnace on/off button on the thermostat off or on it didn’t make any difference it’s still continued to run.
Regarding the AC fan, and with all the jumpers removed, and back to normal, whenever I start the generator if the furnace switch is on and the thermostat is high like 90į, the AC fan will run. It seems like that relay you talked about that Has to either be on cool or heat is stuck on cool. The AC fan starts up since it’s 90į, but if you turn it down to 60 or so the fan will turn off?
Also, when that AC fan runs the AC compressor does not try to run catch up. Remember the switches on furnace not cool. In fact, I can’t get the air conditioner compressor to run with this generator, it’s not big enough. I did try it last summer, it would try to go but made strange sounds and eventually would stalled the generator.
I think perhaps (do you agree) that I should next get a new Tstat. I found one on Amazon that appears to be identical for $30. I just need to check the model nbr.

I am going to take the batteries home with me today, and get them all charged up. Probably order the thermostat. So on my next trip up with charge batteries in a new thermostat will see if anything changes.

Thanks for all your help John.

Ralph
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Old 11-17-2019, 10:34 AM   #18
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Quote:
Originally Posted by relouks View Post
John, in answer to a couple of your questions, yes the furnace burner did come on on both of those test, heat was coming out inside the camper.

And the option three test I had the generator running the whole time. In the option one test I didnít have it running the furnace did start up heat was coming out, but the battery was getting too low and as you said before the fan started going slower and slower, so I started the generator and then went back to normal speed.

In both test I believe the furnace continued to run even if I turn the furnace on/off button on the thermostat off or on it didnít make any difference itís still continued to run.


Regarding the AC fan, and with all the jumpers removed, and back to normal, whenever I start the generator if the furnace switch is on and the thermostat is high like 90į, the AC fan will run. It seems like that relay you talked about that Has to either be on cool or heat is stuck on cool. The AC fan starts up since itís 90į, but if you turn it down to 60 or so the fan will turn off?

Also, when that AC fan runs the AC compressor does not try to run catch up. Remember the switches on furnace not cool. In fact, I canít get the air conditioner compressor to run with this generator, itís not big enough. I did try it last summer, it would try to go but made strange sounds and eventually would stalled the generator.

I think perhaps (do you agree) that I should next get a new Tstat. I found one on Amazon that appears to be identical for $30. I just need to check the model nbr.

I am going to take the batteries home with me today, and get them all charged up. Probably order the thermostat. So on my next trip up with charge batteries in a new thermostat will see if anything changes.

Thanks for all your help John.

Ralph
Hi Ralph,

Good news the furnace is creating heat like it should!!

And yes, on the blue highlight, when you jump the furnace to run, that jumper overrides all T stat and AC unit connections. The furnace is a stand alone system that only needs a run signal to turn on or off. The furnace does everything else on it's own. Under normal working, the furnace relay on the AC board connects or disconnect the 2 wires you were jumping.

Your AC fan running when you start the generator, the temp is 90 or over and the furnace switch is on. And then shuts off if you go below 60. That for sure is not normal.

There is one situation where the AC fan will run when the heat is on, BUT, your system does not have that feature. Well, I say that only by the pic of your T stat as I have never seen the inside of you AC control box area. Dometic offers a 120 VAC heat coil/strip that goes in the ceiling area behind the mesh filter. The Tstat for this has an extra switch for that heating coil. This mode is not running the furnace, only the electric coil. In this case, the fan has to run to blow the heat through the AC ducts. I didn't bring this up before as the T stat in your pics did not have the feature.

BUT, if a prior owner changed the PC board or the T stat there could be a mix up with the wrong part. By any chance is there an electric coil looking device up behind the mesh filter in the ceiling? This is not the exact one for yours, but would be similar and may even be more curved https://www.dyersonline.com/dometic-...strip-kit.html

If your doesn't have anything like that, then yours does not have this heat strip device.

And if it does not have the heat strip device, you are left with the control board is bad, the T stat is bad or some kind of wiring issue tricking the PC board to think the T stat is sending a fan run signal.

The reason your fan only runs with the genny, is the fan is 120 VAC. It will not run unless you are plugged into 120 VAC.

Heads up on replacing the T stat, if you are going to replace it with a Dometic, you have to check the Dometic part numbers that the one you have and the one you are buying are the same. And that it is the correct one for your systems. Pictures on a web site only can sometimes get you to pick the wrong one, even if it looks right. Dometic made a few versions of that kind of looking T stat.

I have no issues with you replacing the same Tstat with a like for like. They did work and had all the switches on them. The only downside to them is regulation quality. If you try and set the temp for say 70F, the swings in temp from turn on to run off could be many degrees apart. +/- 3 to 5 degrees was common, at least when they are older. I never tested a brand new one.

As an option, you can change to one like this, it will do both the heat and the cooling. These regulate with +/- 1 deg. Hunter mod 42999 https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I have done several of these upgrades, they work well in regulating the temp verses the old Dometic analog ones like yours. There is only 2 issues with them,

1. They use 2, AA batteries where the Dometic created its own 7.5 volts. You need to change the batteries once a year. It might go longer, but not a lot longer. Best to change on routine with the smoke detectors annually and have spare batteries on hand.

2. There is no fan hi/lo switch. Many folks just wire it up for hi fan and never add a lo switch to it. If you want the hi/lo feature, then you have to add a additional small switch to jump hi which creates lo. Not hard to do, but needs to be done if you want hi/lo feature.

Now to sort out, is it the AC PC board that is bad or the Tstat or both or a wiring issue.

You can try this to see if the T stat is sending the fan run signal OR the AC control board is doing it on it's own or a wiring issue.

Run the genny so you have 120 VAC

Take the cover off the T stat, make sure the Fan switch is on Auto, turn T stat onto heat, set it at 90 F. See if the fan runs. Want to make sure the problem is repeating itself. And hoping now it will run.

When the fan is running, carefully unhook the FAN wire off the T stat. It should shut off. If it is still running, then the T stat is not sending the signal, and either the PC board has issues or there is a wiring problem grounding out the fan run wire somewhere.

Then you can rule the Tstat out or in of the problem. Next is a wiring issue. Find the color of the FAN wire from the T stat up in the ceiling by the AC control box that is wire nutted. I think yours is orange by your pics. If you unwire nut that orange wire and the fan still runs, then the PC board is more than likely having issues.

Need to know model number off the silver AC control box up in the ceiling to look up the PC board that goes with it.

Hope this helps

John
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Old 11-18-2019, 08:58 PM   #19
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John, I will try that test on the AC fan of unhooking the fan wire next trip up which will probably be Friday the 22nd.
I did order that Dometic tstat. It is the same model number so should be identical. I don't really want one with batteries in it as it is outside in zero weather and don't think the batteries would hold up much.


I got one photo of the AC Box but probably hard to tell much. I did get this info off it. The circuit board is a Watsco Components Inc board. On the top of the board are the numbers 3106996 022 and on the next line 9730. Don't know if one of those might be a model number or not.


I should have the new tstat on next trip up so after doing that AC fan test on the old one, I'll install the new one and see if things improve or change.


Ralph
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Old 11-18-2019, 10:19 PM   #20
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Hi Ralph,

The control box model number we normally use is on the control box, then look it up in the service manual and come up with a Dometic part number.

See here on one of my camper analog boxes. Yours might even be the same as this pic.


It seems Dometic keeps changing who is making their PC boards.

But... sometimes they do add their part number on the board. And in your case, you got lucky. You came back with these numbers off the PC board
Quote:
Originally Posted by relouks View Post
I got one photo of the AC Box but probably hard to tell much. I did get this info off it. The circuit board is a Watsco Components Inc board. On the top of the board are the numbers 3106996 022 and on the next line 9730. Don't know if one of those might be a model number or not.
The PC board out of my older analog control boxes is: AC unit control board Dometic pn 3106996.022. That lines up with the number you came back with. So that is the board yours would use, if you need it.

Last March (2019) I bought one of them off Amazon for $50.46 with tax on Prime. It was sold by Boat and RV Accessories. Well I looked them up tonight and it is now selling for $75.95. I have no idea on how Amazon pricing works.
https://www.amazon.com/Dometic-31069...-items&sr=1-49.

If you go direct to Boat and RV accessories selling it direct, it is $48.99 + tax and shipping. That is still cheaper then the Amazon prime price from the same place.
https://www.boatandrvaccessories.com...elay-board-kit

If you do a search on "AC unit control board Dometic pn 3106996.022" There are a lot of places selling it and the prices are all over the map.

They also sell these on Ebay and other RV parts places.

Good luck and let us know how it goes.

John
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Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC

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1998 sunline, furnace not starting


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