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Old 06-24-2009, 10:06 AM   #21
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Does anyone have a complete list of the CSA specific requirements?

It might be interesting to see if there are any requirements regarding the AC and/or heat.

Also, when installing the Hunters in a CSA tt, does the regular propane heat work OK off the new thermostat?
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Old 06-25-2009, 06:50 PM   #22
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Since we keep our trailer at a storage lot, It is going to be a few days to a week before I can get back to this project.

John, although I know what you are saying about the line draw, honestly I can't see this as being a big issue, especially since the stat is only using the ground wire to switch relays and no real voltage is running through the stat. Perhaps you can also measure the draw on your stat between the ground and the compressor wires so we have something to compare against.

Since I was able to run the compressor through the stat with out the jumper wire in place but not the fan motor. I have to think this is the clue as to what the problem is. I can't help thinking that a wire between the thermostat and the A/C unit is somehow damaged. I think the only way I maybe able to proof this is to run a new temporary line between the stat and the A/C unit.

With regard to the schematic of the board, I assume you are taking about the Thermostat circuit board. If this is the one you are referring too, I have one that came in the Sunline manual. I would assume it was included in all manuals. If this is the one you are referring too and you do not have one in your manual, please PM me with your e-mail address and I will scan my copy and send it to you.

Steve, sorry but I do not have any information on what the CSA standard is for A/C and heating units, however I find it hard to believe there is any difference between the CSA code and the US code. The reason I say this, is the instructions for home thermostat installations appear to be the same in Canada and the US. Also I have installed the Hunter thermostat in other manufactures CSA model trailers in Canada and it has worked without any issue.

With regard to your question regarding the propane furnace, yes it does work without any issues on the Digital thermostat.
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Old 06-25-2009, 10:18 PM   #23
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Trailblazer

I will measure the current for you. Good thought. However I am away on vacation, without the Camper, bummer, and won’t be back until Sunday night.

But to help the cause here, here are some pics from my install. I never yet posted these so now is a good time.

I believe this is the wiring diagram you are referring to in the Sunline Manual. I was after and actual circuit broad schematic on the Hunter so I can figure out what it is doing. .


For those following along here, here is the progression.

The Dometic


How to get the cover off, Gently pry here.


To Dometic board


Close up on terminal strip


Tag with the new color codes before you unhook.


And now unhooked and red power wire cut and taped of.


The new Hunter that I have


Install new wiring plate and jumper


With the Door open to see the controls. I never made it yet to adding the low speed switch


The end results. And it worked well. Regulates to within a degree. My old one was like 3 to 5 degrees pending heating or cooling.



I will have to go back and re-read your post and spilt all those words apart to exactly re-follow. However the jumper….

Here is the part I’m referring to:
Quote:
Originally Posted by Trailblazer
I first connect the yellow A/C wire to the Y terminal, the tan wire to the G terminal and the Green wire to the RC terminal and removed the jumper between the RC and RH terminals.

When the thermostat is set to call for cooling the compressor will kick on but the fan motor does not run.

When the jumper is connected between the RC and RH terminal the Compressor turns off and the fan motor runs. Even after waiting and letting the fan motor run for 5 minutes, even though he stat was calling for cooling the compressor never turned on.

The minute I disconnect the jumper wire the fan motor stops and the compressor turns on. I also get the same results when I connect up the blue high fan speed wire to the G terminal.

Now if I manually connect the yellow, the tan and the green wires together the compressor kicks on and the fan motor runs. JohnB This one step here suggests the wiring should be OK. At least one would think. Remember it worked on the Domectic.

Testing the thermostat, when it calls for cooling the RC terminal. the Y terminal and the G terminal are all connected together. Now what makes no sense to me as to why the connection of the jumper wire between the RC and RH terminal causes the Fan motor to run and the compressor to stop.


Testing the thermostat tells me the only time the RH terminal is in use is when the thermostat calls for heat.
If the Dometic wiring diagram is any kind of accurate for the Hunter, The the fan on - off - auto swith is hard mechanical and not solid state. Since I do not have the hunter diag here, I cannot confrim this. But it is on the Dometic as yoiu can see the sldier switch.

A few questions:

1.With the jumper between Rh and Rc, if you turn on the fan only by the Hunter selector switch I assume that fan runs. This is going thru the hard wiring of the physcial switch to Gnd. Does it work? Yes/No?

2. Now with the fan running by the manual selector switch, then slide the heat/cool switch to cool. Does the fan remain on and the compressor start?

The Hunter solid state output needs to sink the current for both the fan and the compressor at one time when the fan switch is in Auto. By the fan switch bing in manual, the solid state output only needs to turn on the compressor as the fan is already hot wired by the switch.

If neither run when in auto or one drops out, the thought is the solid state output cannot drive both outputs to ground at once. If for some reason your compressor draws more current on the that input then other units, this “might” explain it. I know it's a long shot, but somethign does not add up here.

I will search for the AC unit wiring diagram as that might shed some light on this.

I also have to find on the Hunter on exactly what Rc and Rh do.

We will figure this out, I’m sure of it.

John
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Old 06-26-2009, 12:10 AM   #24
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John,

First off, no worries about not getting to your trailer until Sunday. I am not sure I am going to be able to get to our trailer to run the test this weekend myself.

The schematic you posted is the one I was thinking of. I do not have one on the Hunter Thermostat, but I have done some testing with the multi meter to figure out with stat is doing. Here is what I found:

When the stat calls for heating, the RH and the W terminals are connected together by the stat.

When the stat calls for cooling the G, Y and RC terminals are connected together.

I have not test what happens when the fan switch is set to on, but will this weekend when I get a chance.

When the stat is not calling for heat or cooling and the fan switch is in the auto mode, none of the terminals are connected together.

Now to your question # 1:

1. With the jumper between Rh and Rc, if you turn on the fan only by the Hunter selector switch I assume that fan runs. This is going thru the hard wiring of the physcial switch to Gnd. Does it work? Yes/No?
run.Yes the fan will run

2. Now with the fan running by the manual selector switch, then slide the heat/cool switch to cool. Does the fan remain on and the compressor start?

I have not tested this scenario. Good thought, I have always tried starting the cooling with the fan in the auto position. I will try this the next time I am at the trailer

Now I have a question for you. Looking at your pictures it appears you have wired your stat slightly different than the instructions. Now it may just be the way the colors look on my monitor, but it appears you only have the low speed fan(tan) wire going to the G terminal and that you have the blue high speed fan wire going to the RC terminal. Am I correct.

If you have connected the blue to the RC, I am curious as to why you did this. Generally for hi speed fan only, you would connect the tan and the blue directly to the G terminal?[/i]
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Old 06-26-2009, 07:52 PM   #25
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Ok John, after giving it some thought I understand what you are doing by connecting the blue wire to the RC terminal. Correct me if I am wrong but it is giving you the same effect as connecting it directly the the G terminal and giving you the high fan setting.

I had a chance tonight to head over to the trailer and do some more testing. First, I tried putting the fan on the On setting instead of the Auto setting. Once the fan was running for two minutes I tried turning on the cool setting. Using this setting the compressor would not start.

I next removed the two fan wires. When the cool setting is selected the compressor would start.

So now it is time to take some measurements. First I measured the voltage in parallel when the compressor was running. The meter read 7.5 volts.

Next I disconnected the compressor line and the ground wire. I first connected the two together and the compressor started. I next tried measuring the amps draw. I place the multimeter in series between the compressor wire and the ground wire. I tried measuring both on the amp scale and the mini amp scale. With the multimeter in serious the compressor would not start and I had no amp readings. Now my mind is drawing a blank, what am I doing wrong.

John, I do agree with you the problem has something to do with the draw on the thermostat. It definitely has something to do with the combined draw of both the fan motor and the compressor. If either one starts by itself the thermostat can handle it, but when both the fan and the compressor try to start together, the fan wins and starts while the compressor fails.
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Old 06-26-2009, 10:01 PM   #26
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Trailblazer, we may be gaining….

Quote:
Originally Posted by Trailblazer
Ok John, after giving it some thought I understand what you are doing by connecting the blue wire to the RC terminal. Correct me if I am wrong but it is giving you the same effect as connecting it directly the the G terminal and giving you the high fan setting.
Here is a zoom in pic.


The high speed fan signal is looking for “Gnd” to run. And low speed is un grounded or floating. So since I did not have my hi/lo toggle switch yet, I just tired the blue high speed fan to gnd so it would run hi all the time.

Since Rh, Rc Gnd (green) are all jumped together, I just tied the blue high speed fan to the easiest terminal to connect it to.

Quote:
Originally Posted by Trailblazer
I had a chance tonight to head over to the trailer and do some more testing. First, I tried putting the fan on the On setting instead of the Auto setting. Once the fan was running for two minutes I tried turning on the cool setting. Using this setting the compressor would not start.

I next removed the two fan wires. When the cool setting is selected the compressor would start.

So now it is time to take some measurements. First I measured the voltage in parallel when the compressor was running. The meter read 7.5 volts.
OK what 2 terminals did you get 7.5 volts across? I have been searching tonight for some kind of Dometic 57915 service manual with a “real” wiring diagram. Did a lot of reading…. Not really great wiring diagram, yet. Also Dometic makes a Digital T stat. And it uses a 4 wire phone jack to just plug it in. Which is part of why I can’t find a wiring diagram. It is plug and play. Seems we have the older version of T stat.

Here look on page 50 and 51 of this manual http://bryantrv.com/docs2/docs/acservice.pdf It is like a 3 meg download.

I had another one, but can’t back track into it right now. But will.

I have read so many manuals tonight I can’t backtrack right now to the one I found where it said the min voltage should be 10 volts. But not being able to find it, again... it might have been mentioned it up at the AC unit where the 12 volts DC comes in. So what you are measuring may or may not be OK. I’ll dig some more on Saturday

Quote:
Originally Posted by Trailblazer
Next I disconnected the compressor line and the ground wire. I first connected the two together and the compressor started. I next tried measuring the amps draw. I place the multimeter in series between the compressor wire and the ground wire. I tried measuring both on the amp scale and the mini amp scale. With the multimeter in serious the compressor would not start and I had no amp readings. Now my mind is drawing a blank, what am I doing wrong.

John, I do agree with you the problem has something to do with the draw on the thermostat. It definitely has something to do with the combined draw of both the fan motor and the compressor. If either one starts by itself the thermostat can handle it, but when both the fan and the compressor try to start together, the fan wins and starts while the compressor fails.
First off, is there voltage between the compressor wire (yellow) and ground (green) and what is it?

Your meter, most upper end ones have a fuse in the amp meter circuit in case someone hooks it up wrong or overloads it. Is the fuse OK and do you know the amp feature works? (have to take back of meter off to get to the fuse on many of them.)

I’m sort of handi caped here not having the camper in front of me. The meter should of worked between compressor wire (yellow) and ground (green) unless my brain missed something simple. This is why I wanted and actual schematic of the circuit board. This wire circuit is most likely all DC and it might be a simple Open Collector output NPN transistor in the T stat simply just tying the compressor or fan wire to ground. Basically the fan or compressor will run when it finds the same potential as ground.

I’ll do more digging and report back.

John
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Old 06-26-2009, 11:27 PM   #27
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John, Thanks for the link to the manual. That is quite a lot of reading.

The 7.5v was measured between the cool and the gnd terminals on the Duo-Therm Thermostat. It was also measured between the Y and the RC terminals on the Hunter thermostat. Based on what link to the manual reads, I would agree this appears to be ok. I will have to check the voltage across the other terminal points the next time I am back at the trailer.

As far as the multimeter goes, it is just a cheap one I keep in the trailer. I will have to take the back off to check the fuse the next time I am at the trailer.
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Old 06-27-2009, 07:49 AM   #28
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Quote:
Originally Posted by Trailblazer

As far as the multimeter goes, it is just a cheap one I keep in the trailer. I will have to take the back off to check the fuse the next time I am at the trailer.

Just a friendly reminder in case you forgot, on current on most meters you have to move the test leads plug to allow amps to work. The common may be the same but you have to move other lead to the amps port.

Good hunting. I'll do some reading/digging.

John
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Old 07-01-2009, 11:46 PM   #29
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Here see if this helps. I’m going camping Thursday and will fiddle more when I have 30amps on the TT to run the AC.

But for now, this much is known. There is a PC board relay on the Hunter doing the switching. No solid state interface with the AC unit. Which makes sense they use dry contacts as the interface.

The relay is a Omron G6SK-2 2 pole latching relay.

http://www.onlinecomponents.com/prod.../mf-OM/G6S.PDF

http://www.components.omron.com/comp...ID=CNEN-6SUP6G

The pin out looks like this.


Pins 8 and 9 are used on the Cooling contact which is a normally open contact. 8 goes to Rc, 9 goes to Y.

Now here is some more. The infamous Hunter diagram.


And better yet, the PC board on my spare Hunter.






I traced out the wires. The Heat – off – cool switch and fan switch makes certain circuit paths. They are hard mechanical switches. The Yellow wire scribble is the relay contact when the T stat calls for cooling.


I labeled the pins so we can see where the wiring is going.

There is also a slider switch on the PC board that changes the fan operation. Look in the lower right corner of the brown board side in the pic above. You will see it when you take the T stat off the wall. It has 2 positions, HG and HE. The instructions says it is only used for some heating systems but it is in the same wiring as the cooling. If you slide it from Hg to He it will change the fan operation. If you are out in the camper, try sliding it to He and see what happens. It might help or it might just turn the fan on all the time on cooling. If it actaly helps you, just check what it does on heat as well.

The rated load of the Omron relay is 2A at 30 VDC. There should be no problem running the compressor and the fan thru that same contact on the Hunter.

At least we know what it is not now. There are no solid state outputs in the hunter turning on the AC unit. It is just a relay.

Be back with more soon.

John
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Old 07-02-2009, 08:39 AM   #30
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Atwood Thermostat

JohnB and Trailblazer may be way ahead of me already, but I learned a couple of things while visiting my brother over the last week. His Titanium has a CSA certified Atwood digital thermostat installed at the factory. This thermostat is very different from the Hunter in that it has no battery and uses the 7.5V wire as well as a second 12V one--it's also at least 5X the price. The thermostat in the Titanium is Model 2H2C for a two stage furnace. They also make Model 1H2C for single stage, which I believe is what the Sunline has.

This is the link to the Atwood page:
http://www.atwoodmobile.com/heating-...hermostat.aspx

This page has links to the two thermostats in the right hand column which will open a pdf if your browser is set to do that, or you can click on the links here:
http://www.atwoodmobile.com/media/38...thermostat.pdf
http://www.atwoodmobile.com/media/37...thermostat.pdf

You may find the wiring diagrams helpful in figuring out what is going on. I am also still somewhat skeptical that CSA could cause this kind of a problem, but am impressed by the prominence of the CSA compliant label right at the top of the Atwood documentation.

Another link I came across in Google is to a home thermostat that has manufacturer's instructions for RV installation:
http://www.ritetemp-thermostats.com/RVs.html

Henry
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Old 07-02-2009, 09:25 AM   #31
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John,

Your extensive dissection of the Hunter is awesome. It leads me to wonder about a few things that might easily be checked in TrailBlazer's unit.

First, because the Hunter in question is a digital mechanical thermostat (I read that on the package in Lowes yesterday... ) it rules out a lot of electronic things. In my mind, that leaves:
#1. A defect in the thermostat itself, probably either the relay or a trace or solder joint on the circuit board.
#2. A defect in the cable between the AC and the thermostat.
#3. A defect in the AC itself.

I would tend to rule out #2 and #3 because the regular DuoTherm works OK.

Leaving #1 as the apparent only area to be looked at. If the HG/HE switch doesn't solve the problem, then...

TrailBlazer, do you have access to another Hunter that you could try? That might answer a whole bunch of questions.
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Old 07-02-2009, 09:49 PM   #32
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Sorry I haven't posted any results lately. It is just that I have been busy and not back to the trailer since last Friday night. We are going away camping this weekend so I will take the amp measurements this weekend. I will also try changing the position of the HG/HE switch and report back. Right now it is set on HG. I know this for a fact because this was one of the first things I checked when the compressor would not turn on.

Steve, with regards to trying another Hunter Thermostat, I have borrowed a friends that works in his trailer and tried it in mine. My friends thermostat would not start the compressor in my trailer either. Place back in his trailer the compressor would start without a problem.

While camping this weekend, if the weather permits, I plan to go on the roof of the trailer and remove the A/C shroud to take a look to see if I can notice anything different. I also plan to clean both the Evaporator and Condenser coils. I have been told that dirty coils can result in up to a 2 amp higher current draw.
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Old 07-05-2009, 08:10 PM   #33
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I did try again this weekend after cleaning both the condenser and evaporator coils. Still no luck getting the compressor to run. I also tried moving the HE/HG switch to the HE setting. Again this made no difference. I was not able to test the amp draw through the thermostat.

Anyways, sorry fellas, but I have spent too much time on trying to get the thermostat to work this year, so unless someone comes up with answer, I am going to have to shelve this project for another by.
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Old 07-06-2009, 02:11 PM   #34
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Trailblazer,

Hang in there Curosity now has the best of us and you too I'm sure. Us with inquiring minds, need to know....

This weekend out camping I took a bunch of readings for you to compare too. I know more of what it "should not be" or at least for you to go looking for.

I'll be back soon with pics and even more into the actual Dometic T stat as I have figuired out how it works. As to why it works but the Hunter does not???

The HE/HG slide switch, ah nope that won't help. I tried this too this weekend. Sorry for the miss lead. It does like the instructions says. It works on the furnace side. If you are hooking this up to a forced air electric or gas furnace it will turn on the fan when it turns on the heat control. I treid it on heat. The AC fan runs when the furnace kicks in, in a camper that is not CSA standard that is.

Be back with more soon.

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Old 07-06-2009, 06:46 PM   #35
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Quote:
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Trailblazer,

Hang in there Curosity now has the best of us and you too I'm sure. Us with inquiring minds, need to know....
Actually I have spent way too much time on this one and I have other things that I need to do. Unfortunately every time I start looking at the Thermostat, by the time I am done I don't feel like tackling any of the other projects I need to do. Therefore, i need to shelve this mod for a little while. Besides, DW is starting to get tired of me always taking the T-stat apart and getting in her way in the trailer.

If you come up with a brain storm and you want me to look at it, just let me know, otherwise I am going to be working on other projects until then.
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Old 07-06-2009, 09:33 PM   #36
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OK see if this helps. I guess this is the brainstorm when ever you get to it.

This one really had me interested this weekend and I tested the new and old in several different ways trying to help figure this out. See the end for Summary questions.

First I said, well just how is the old Dometic T stat working? Trailblazer said it works on that unit. Is this correct? And is it this Duo-Therm unit I have here?

I tried to find out if they have a CSA version but I cannot seem to track that down.

http://www.dometic.com/enus/Americas...ctdataid=66942

I “think” what I have is a Dometic 3106995.032. I can find then on sale on Ebay from $40 to $5.00….

So this is what mine looks like and my late 1970 electronic skills still work…..or at least what I remember.


The back of the board looks like this.


Here is the basics of how this works.

There is a temperature sensor on board, about the same as in the Hunter. When you blow different temp air across the front of it it’s resistance changes. The temperature control slider that you move to change the inside temp is a linear potentiometer. The brain of this thing is a OP Amp chip.

When the room temp as sensed by the temp sensor resistance lines up with the adjustable slide pot resistance, the OP amp turns on an output. That output then drives both the heat and cool NPN transistors base drive active at the same time. The NPN transistor is a sinking type so it will connect the wire terminal called cool or heat to gnd (DC common).

The selectors switches, “cool –off – heat” then connect the wiring terminals to the corresponding output. So even while both transistor outputs are on at once, it does not matter as the sel switch does not connect the heat or cool signal to the AC unit or the furnace.

The fan when in auto just follows the Cool output signal. The fan ON, is a hard wired override. There is no transistor for the fan.

Here are some links if you want to drill down into the electronics more. Or I have other old books at work I can scan.
The TI LM2409D http://focus.ti.com/lit/ds/symlink/lm2904.pdf

The Fairchild MPSA06 http://www.fairchildsemi.com/ds/MP/MPSA06.pdf

So that is the basics of how it works. Now to how it measure in voltages.
I took the Hunter off and used the taped off 7.5 VDC hot line and powered up the Dometic. The green jumper is going to the Dometic GND term. I get 7.28 VDC running this coming out of the AC unit.


Now to the fan output while on Auto. I connected an ohm meter between Fan and gnd to see how much resistance there was in relation to Gnd. A whopping 11.5 ohms


Now to the cooling output. I connected an ohm meter between Cool and gnd to see how much resistance there was in relation to Gnd. A whopping 11.6 ohms


Now I flipped to voltage on the Hunter back plate. Here there are 2 voltages going on.

The Fan G volts to Gnd. 12.32 VDC



The Cool Y volts to Gnd. Oldy enough this is 8.03 volts.


And now the Heat W volts to Gnd. 12.32 VDC again.


Now I did the input resistance to Gnd
The Fan G ohms to Gnd. 0.836K ohms


The Cool Y ohms to Gnd. 16.14K ohms


And now the Heat W ohms to Gnd. 0.814K ohms


And now it is time for current.
The fan on it’s own G to Gnd. 28.14 mA. The fan is running with the meter connect this way in series.


Now the compressor only, Y to Gnd. The compressor only is now running with the meter connected this way in series. 1.49 mA


And now both fan and compressor tied together and then in series with the am meter to gnd. G & Y to gnd. 29.34 mA.


Basically if I just jump G, Y and GND all together the Fan and Compressor run. No T stat.


A close up of the jumpers


Now to the AC unit input board. Here I could not easily figure out how to get the cream colored plastic shroud off to get the entire sticker.


The wiring to the T stat


So I now said well OK what is the Hunter doing. I connected and ohm meter on the table to the contact and forced the temp to bring the outputs on.

First the slide switch to turn on the fan. Rc to G. 1.7 ohms


Now the Fan on Auto using the relay in side. Rc to G 3.7 ohms


And The cooling output relay to Gnd. Rc to Y 2.8 ohms


While the relays in the Hunter add a tiny bit of resistance, there is practically none.

So here is the Summary:

If you jump G (Fan), Y (cooling) and Gnd all together on the Hunter plate does the fan and compressor run? I assume yes but you confirm.

Does your volts, ohms to ground and current match mine on the Dometic?

If you have the Hunter on the table and do a ohms check between Rc and G and Rc and Y do they come up less the 10 ohms?

The Hunter relays can handle the current. Heck they are rated at 2.0 amps. The NPN transistor of the Dometic is like 0.5 amp rating and the system only uses less then 30 mA when the fan and compressor are running on the signal lines.

This is not a current component issue, at least by design. When you where cleaning the coil on the roof. (thanks by the way for the links, I need to do that) that cleaning may have lowered the entire AC unit power draw. It should not have any affect on the control board side. So you did a good job on cleaning it, just it would not do much for this mystery issue we are now facing.

If there is something in the CSA standards on preventing the Hunter from working, it is really got me now. If the wall plate jumped out runs the fan and compressor, the wiring is fine and so is the AC unit. The Hunter should run it.

OK tell me what does not check out or what is different in what I have verses yours?

Again not pushing, when you get to it. You know you want this to work and some day the curiosity will get you again and you will figure this out. And trust me, when it does work it is night and day better then the standard Dometic analog unit.

By the way, I had all this checking stuff in my truck at the M & G. It is part of my work kit that always camps with us. We should of both stood there and tried to go over this in your camper. This one really has my curiosity up. Plus I’m learning a whole lot about my AC unit I never knew…. It always worked so I never had to do much with it.

PS From Henry’s link I found out the Rc and Rh are split in case a system needs independent DC commons. So in our case we jump the 2 together as it is one DC common.

Hope this helps

John
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Old 07-20-2009, 09:10 PM   #37
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Although I have been busy with doing other mods on my rig such as adding a water filter and working on building my own water accumulator tank, I have continued thinking about and researching this mod. Recently I have come across the rite temp thermostat site where they have the following wiring diagram.

Now this one is different in that it does not use the jumper between the RC and RH terminals, but in fact treats both the heat and A/C as two separate systems. Now what I am thinking is the Ground gets connected to the RH terminal and the white wire to the W terminal. Next the 7.5v gets connected to the RC terminal with the yellow to the Y and the tan and blue to the G terminal.

Do you see any danger in hooking up the thermostat using this method. Do I have any chance of creating a dead short and frying any wires or the circuit board.

How can I test or prove this with a multi meter without actually wiring it this way
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Old 07-20-2009, 09:37 PM   #38
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Trailblazer

Using the Hunter as an independat common between heat and cool, I do not see as a problem. They are relay contacts. Totally isolated.

However I have to draw out your color word wiring to figure out what you are saying.

I do not know what you are using the 7.5 volts for. What are you trying to power with that?

The AC unit needs 12 VDC from the battery or convertor to run the control board. The furnace needs 12 volts DC to run as well, both use the same DC common.

I'll map out yur wires words into a diagram and report back

John
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Old 07-21-2009, 12:04 AM   #39
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What I am wondering is if the A/C actually needs the 12VDC+ where as the furnace needs the 12VDC-. I am wondering if this is the difference between the Sunline US models and the Cdn Models.

Is it possible that it is a fluke that we are getting the compressor to run when we connect it to the 12VDC- and that is somehow back feeding from the 12VDC+. Thinking out loud, that when we then connect the fan motor as well as the compressor the 12VDC- back feed can't handle both units and why only the fan motor runs. Not sure if I am explaining this well enough.

I know this is a long shot, but it is the only thing I can think of that might be different between the US and Cdn models. I guess the real test would be to jumper the fan, the compressor and the ground wires together to see what happens.

Ideally, if we could find an A/C wiring diagram on the Cdn model and then compare it to the one on you posted from the US model we could see if there is a difference.

Anyways, I am still not going to be able to work on any of this for several more weeks, but thought I would post this new T-stat wiring diagram that does not have the RC and RH connected together for comment.
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Old 07-31-2009, 09:27 PM   #40
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Hi Trailblazer,

Sorry this took so long but I knew you said you where weeks out.

First off you said

Quote:
Originally Posted by Trailblazer
I have continued thinking about and researching this mod. Recently I have come across the rite temp thermostat site where they have the following wiring diagram.

Now this one is different in that it does not use the jumper between the RC and RH terminals, but in fact treats both the heat and A/C as two separate systems. Now what I am thinking is the Ground gets connected to the RH terminal and the white wire to the W terminal. Next the 7.5v gets connected to the RC terminal with the yellow to the Y and the tan and blue to the G terminal.

Do you see any danger in hooking up the thermostat using this method. Do I have any chance of creating a dead short and frying any wires or the circuit board.

How can I test or prove this with a multi meter without actually wiring it this way
Do I see danger in putting + 7.5VDC on the RC terminal? Yes that I do, at least on the US unit I have. On my system that would create a dead short.

See here on how the old Dometic wiring goes. At least on my US system. The 7.5DC is to run the PC board. It does not power the AC unit. I traced out the Dometic PC board and it is a pure and simple old fashion NPN transistor sinking output. When the transistor base drive has a higher potential then the emitter, the collector will allow a path to DC common. Basically it is a DC sinking switch. It takes the compressor run signal and connects it to DC common. The cool wire from the AC unit input board up in the cieling is looking for a path to DC common to complete the input. It can have a voltage on it floating until that Yellow wire finds a ground, then it completes the input signal. OR The cool (Y) wire floats neutral when the transistor is not energized. Either way it is lookgin for gnd to turn on.

Here see this cryptic wiring diagram. The 7.5 VDC runs the PC board.



If you put the +7.5VDC right on the cool line (yellow) that will make that wire hot. Now trace the wiring path. You said put the Tan (fan signal) and blue (hi fan) to G. (ground.) If you flip the fan switch from auto to ON, you just created a part dead short from the +7.5VDC to the G terminal. . And if you follow that + 7.5VDC thru the Auto switch, the other end of it comes out the Tan (fan) terminal that just went to ground. Both of these combo’s create a short of the 7.5DC to ground. Again on my US unit.

I do not know what the back feed the +7.5 source will have on the Yellow (cool) input up in the AC unit. Did not dig that far.

Now to next post

Quote:
Originally Posted by Trailblazer
What I am wondering is if the A/C actually needs the 12VDC+ where as the furnace needs the 12VDC-. I am wondering if this is the difference between the Sunline US models and the Cdn Models. .
On my US version I for sure must have the +12VDC on to the AC unit or it will not run. I tested this. I have not posted this yet, but will. I did the coil cleaning complete with pics and amp probe checks before and after. I took your lead and just pic documented it along the way.

After pulling the cover off on the roof and seeing the compressor starting capacitor, I got to thinking and measuring. I can run my AC unit off my Honda e2000i. BUT it takes certain things in place as I cannot run anything else, and I mean nothing. I would only ever use this as a last resort in a sweltering situation when boon docking. That is until I get my Companion Honda to get 4000 watts. But that is not this year.

Point is, I shut down the entire converter and had the battery off, no linve +12DC. The only thing live in the camper was 120VAC and only the AC breakers on where the main 30 amp and the 20 amp AC unit. All the rest of the breakers where off. The AC unit did nothing.

I then turned on the battery to bring the 12VDC alive still leaving the convertor off. Now the fan would run on the manual switch and then I would flip on the compressor. This way I only had the compressor inrush to deal with on the Honda. Not fan and compressor and no converter robbing overhead as well. And the Honda was not on ECO mode. So again on my US unit, the +12DC has to be on in order to run the A/C (Air cond) controls.

Quote:
Originally Posted by Trailblazer
Is it possible that it is a fluke that we are getting the compressor to run when we connect it to the 12VDC- and that is somehow back feeding from the 12VDC+. Thinking out loud, that when we then connect the fan motor as well as the compressor the 12VDC- back feed can't handle both units and why only the fan motor runs. Not sure if I am explaining this well enough.

I know this is a long shot, but it is the only thing I can think of that might be different between the US and Cdn models. I guess the real test would be to jumper the fan, the compressor and the ground wires together to see what happens.

Ideally, if we could find an A/C wiring diagram on the Cdn model and then compare it to the one on you posted from the US model we could see if there is a difference.

Anyways, I am still not going to be able to work on any of this for several more weeks, but thought I would post this new T-stat wiring diagram that does not have the RC and RH connected together for comment.
On my US unit, I jumpered cool (yellow), fan (tan), Hi fan (blue) to G, ground and the entire system started up. Here is the pic. I am running the complete system with no T stat.




The Hunter being a dry contact relay output is doing nothing more then hooking up my jumpers to DC common.

If you jump cool, (Yellow), fan (Tan) and hi fan (Blue) to ground (G) and the entire system runs, the Hunter should work. The Hunters output relay has many times over the current capacity of the US Dometic NPN transistor. If the jumper test does not work, then something is really not adding up. Next time we are in the same campground together we both have to look at this thing at the same time….. Can you make the ADK meet & Greet? I’ll be there.

Hope this helps

John
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