'81 Sunline 15.5 SB HF-8012 Won't Blow or Start

[SSF156]

Any idea why my Hydro Flame HF-8012 furnace won't blow? It's connected and the thermostat is set to on. I read the manual. I pressed the sail switch after waiting for the unit to click, this was after turning the thermostat to on. See the link for a video here: https://photos.app.goo.gl/WsawT2FXKMUbYEQ6A

Thanks in advance!

[JohnB]

Hi,

I saw your video, and after clicking it a few times, it started to work for the full minute you recorded, which helps.

You have what looks like the HF-8012 P version. They made a P for pilot and a D for direct spark ignition. Look at the white label for the P or D after the HF-8012 if there is a P or D. It appears you have the pilot version by your gas valve and what looks like the Piezio igniter button next to it.

Please confirm I have that right; you have the P version, which requires you to start the pilot manually.

You stated this in your post.

I pressed the sail switch after waiting for the unit to click, this was after turning the thermostat to on.

Sorry, but you may have a typo or misread something. You said you pressed the "sail switch". The sail switch is a safety device inside the furnace bower housing that closes its contact when the fan motor is running fast enough to allow the gas valve to be open and start ignition. You should not have had to touch the sail switch.

However, as you asked, the fan motor must run first, regardless of your version of the gas burner ignition. You need to sort that out first.

A few questions to help where to start on this so we can help better.

1. Please look for the D or P after the model number and post so we know that.

2. Has this furnace run since you bought the camper, or is this the first time? We need some history to determine whether it stopped working or if this is your first time trying to get it to work.

3. Since the fan motor will not run when you turn on the T stat switch, we must first get the fan to run before lighting the gas burner.

3A. Did you slide the T stat temperature to the highest setting to create a call for heat? Yes/No? The T stat has to call for heat even if the fan is on and the switch is on.

3B. If the T stat is turned full up in temperature and the T stat is turned on, the fan motor should start after about 15 to 30 seconds. If it does not, then:

- Check that the fuse in the camper power center is not blown for the furnace.
- If your furnace has a circuit breaker on it, see if that breaker on the furnace is not tripped. The wiring diagrams show one on the furnace, but I'm not sure if yours has one or not.

Please comment on the above questions and try step 3 to see if the fan starts to run.

If the fan still doesn't run, the next step is to start electrical troubleshooting if this is within your skill level. You will need a 12-volt test light or a DC volt meter, know how to use them, and have worked with electricity and how to work safely around it. If power reaches the furnace, a thermal timing relay runs the fan control, which may have failed; the fan motor itself may be bad, or some other wiring connection issue. Before we get into that, let us know the above info we asked.

PS, I'm not sure which furnace manual you have. I have an old one, but we have a member uploaded one that has more in it than the one I have. See here, in our files section https://www.sunlineclub.com/forums/d...o=file&id=5566

Here is my 8-pager one; it still mentions the same things with less info. https://www.sunlineclub.com/forums/d...o=file&id=5652

Let us know if your manual is different.

I hope this helps,

John

[SSF156]

John,



See my responses quoted below in red.

Originally Posted by JohnB

Hi,

I saw your video, and after clicking it a few times, it started to work for the full minute you recorded, which helps.

You have what looks like the HF-8012 P version. They made a P for pilot and a D for direct spark ignition. Look at the white label for the P or D after the HF-8012 if there is a P or D. It appears you have the pilot version by your gas valve and what looks like the Piezio igniter button next to it.

Please confirm I have that right; you have the P version, which requires you to start the pilot manually.

You stated this in your post.

Sorry, but you may have a typo or misread something. You said you pressed the "sail switch". The sail switch is a safety device inside the furnace bower housing that closes its contact when the fan motor is running fast enough to allow the gas valve to be open and start ignition. You should not have had to touch the sail switch.

However, as you asked, the fan motor must run first, regardless of your version of the gas burner ignition. You need to sort that out first.

A few questions to help where to start on this so we can help better.

1. Please look for the D or P after the model number and post so we know that.
I believe it is a P, as you denoted. There is a push button which clicks to start the pilot.



2. Has this furnace run since you bought the camper, or is this the first time? We need some history to determine whether it stopped working or if this is your first time trying to get it to work.
No, it has not ever run during the time I've owned it since October 2024.



3. Since the fan motor will not run when you turn on the T stat switch, we must first get the fan to run before lighting the gas burner.
Sure, I was attempting to start this on Shore Power but attempting to run it off of the 12-V battery was also unsuccessful. The lights dimmed inside my camper and almost became dark. No luck.


3A. Did you slide the T stat temperature to the highest setting to create a call for heat? Yes/No? The T stat has to call for heat even if the fan is on and the switch is on.

Yes, I had it up as high as possible.


3B. If the T stat is turned full up in temperature and the T stat is turned on, the fan motor should start after about 15 to 30 seconds. If it does not, then:

- Check that the fuse in the camper power center is not blown for the furnace.

Where can I find this fuse panel? I have a 1981 Sunline 15.5 SB.

- If your furnace has a circuit breaker on it, see if that breaker on the furnace is not tripped. The wiring diagrams show one on the furnace, but I'm not sure if yours has one or not.

<s>Could you possibly direct me to where the breaker would possibly be? </s> I will check this soon.


Please comment on the above questions and try step 3 to see if the fan starts to run.

If the fan still doesn't run, the next step is to start electrical troubleshooting if this is within your skill level. You will need a 12-volt test light or a DC volt meter, know how to use them, and have worked with electricity and how to work safely around it. If power reaches the furnace, a thermal timing relay runs the fan control, which may have failed; the fan motor itself may be bad, or some other wiring connection issue. Before we get into that, let us know the above info we asked.

PS, I'm not sure which furnace manual you have. I have an old one, but we have a member uploaded one that has more in it than the one I have. See here, in our files section https://www.sunlineclub.com/forums/d...o=file&id=5566

Thanks! I will give this a look!

Here is my 8-pager one; it still mentions the same things with less info. https://www.sunlineclub.com/forums/d...o=file&id=5652

Let us know if your manual is different.

I hope this helps,

John

[JohnB]

Hi,

Here are some comments, to your responses in red

3. Since the fan motor will not run when you turn on the T stat switch, we must first get the fan to run before lighting the gas burner.
Sure, I was attempting to start this on Shore Power but attempting to run it off of the 12-V battery was also unsuccessful. The lights dimmed inside my camper and almost became dark. No luck.

Well, there is good news and bad news about your battery situation. The good news is that if the lights were dim, there was some connection between the battery and the camper for the power to get to them. This means the primary battery fuse between the battery and the main camper fuse blocks is still intact.

The bad news is that you either have a close-to-dead battery you are using, or there are issues inside the camper creating a heavy current load. More on this in a moment.

Next comments

3B. If the T stat is turned full up in temperature and the T stat is turned on, the fan motor should start after about 15 to 30 seconds. If it does not, then:

- Check that the fuse in the camper power center is not blown for the furnace.

Where can I find this fuse panel? I have a 1981 Sunline 15.5 SB.

- If your furnace has a circuit breaker on it, see if that breaker on the furnace is not tripped. The wiring diagrams show one on the furnace, but I'm not sure if yours has one or not.

Could you possibly direct me to where the breaker would possibly be? I will check this soon.

As we would call it nowadays, the camper power center in older campers is very different from the more all-in-one power converters with fuses and circuit breakers in an all-in-one case. The older Sunlines were built from separate components.

Here is close to what you are looking for: Find the power cord outside the camper where it enters the camper wall. Go inside in that general area where the cord enters the camper. Look inside a cabinet, under a dinette, bed, etc., but it would be on the floor. You should find a separate circuit breaker box for the 120 VAC items. Then, a fuse block with glass fuses separately. There would also be some form of stand-alone battery charger/power converter. These pics are from a 1979 Sunline from SunlineFan's camper. Yours, being a 1981 camper, could be very similar or the same. But the locations of these items change per floor plan. I do not exactly know where yours is, as I or others do not know every floor plan made, but we can help as we know somewhat was done as the years went by. I am fluent in the newer Sunline campers, learning daily on the oldies and helping others. This is the post these pics came from. https://www.sunlineclub.com/forums/f...tml#post147243

The 120 VAC breaker box looks like this


You may find some power converter, the brown box on the floor, SunlineFan's looked sort of like this, but someone may have changed the original on his as it does not look like other 80's campers I have seen


Here is a fuse block, but this is for the DOT lights on the camper. (the tail lights, marker lights etc. On the older campers Sunline fused them


The fuses protect the furnace, lights, water pump, and other components, most likely inside your power converter. Here are pics from a 1987 camper inside the brown converter box with the glass fuses that run inside the camper. I'm not sure if your has this or not being a little older. in this case, the large red wire is battery + Pos, and the large white wire is battery - neg.




Look in your camper for items that look like the above. A previous owner may have changed something. Take good pictures of what you have and post them, and we can help you sort it out.

Now, regarding the furnace, it will not run unless you have good 12 VDC power, and if your lights dim, that is not good power. There may still be something wrong with the furnace, but until you get a good 12-volt DC power to work in the camper, the furnace will not work. You will need between 12.5 to 12.7 volts DC or higher as a starting place for the furnace. If your power converter works when you plug into shore power, it may raise the voltage. It may be up to 13.6 VDC. If your volts are down in the 12.0 range, that is too low to try and run the furnace; when the fan motor runs, the voltage will drop a little as it is a larger power draw.

The battery you want is a 12-volt deep cycle battery, not a starter battery like in a car. Walmart sells deep-cycle batteries that will work in some auto or farm stores. The standard size Sunline installed was a case size, group 24 deep cycle battery. You can buy bigger ones, but then the plastic case and where it fits on the camper A frame may need to be modified. And the camper is set up on negative ground. The negative (-) terminal is common to the camper frame and wired to the inside as ground. The positive (+) terminal is the hot wire and is not common to the camper frame. The battery wires' colors have changed over the years, and a prior owner may have changed them. Trace out the negative cable and look under the camper to see if it is attached to the metal frame and the LP gas pipe. That color wire is the negative.

Do you have a 12 VDC voltmeter and know how to use it? Or have a buddy who works on auto's electrical or home 120 VAC power; they can help you sort this out. You start at the battery and check the battery voltage unhooked from the camper, then hook up the battery and see if the voltage drops instantly by a lot. If there is no significant drop, go inside the power converter and test the fuse blocks to see what power is getting inside. In 12-volt circuits, a 1-volt drop is a significant number.

I hope this helps. Let us know how it goes.

John

[SSF156]

Turns out the fan motor has not run for white some time. I spun the fan and it started right up. Now I am having issues getting the pilot started. Help? I have gas going to the oven.

[JohnB]

Hi,

It seems your pilot will not work. This gets more complicated on these older furnaces when the gas valve and pilot do not work. Parts are scarce, but some may still be available. We can get to that, but we will need more information from you to help better.

If this furnace has not run in a long time or years, other issues beyond the gas valve should be checked and verified to be OK before trying to light it. When I restore a 15 to 20-year-old camper (yours is lots older at 44 years), I pull the entire furnace out and go through it to ensure no insects or other critters have crawled in and made a home in the combustion chamber. Or mice left over things on the inside area of the furnace. Yes, both have happened. And rust on the heat exchanger to ensure there are no holes to leak fumes inside when the system is running. This also includes a close inspection of the controls and an LP gas leak test before I fire it. This is all in a bench test setup out in the open. Corrosion on the aluminum of the gas valve is common on the newer models (20-year-old versions), and the valve seat inside can be corroded and will not seal off and pass a leak test. In this case, I can get parts to replace the whole valve.

I'm not sure if you're familiar with LP gas controls or the test equipment you have. Do you have a buddy who is an HVAC tech? They would have all the needed equipment and could help check out the unit with you.

If you can explain on the pilot what you have tried and what does or does not work, it also helps. That and pictures on the complete name tag, when you take the brown grill off, along with photos of the condition of the gas valve and the blower, controls as a start.

If you have no gas flowing to start the pilot, assuming you are following the right directions on how to light it, then we have seen here on the forum that the gas valve portion for the pilot may be gummed up and blocking the flow, or the valve itself may have issues. Sometimes, they can get them to work, other times not as they can't get parts as something broke trying to take them apart to clean the valve passages.

I'm not saying your furnace can't be fixed, but I'm trying to express friendly caution about ensuring it is fit to run. If it comes to be, you need an all-new gas valve with the pilot control, which may be a hard find.

Tell us and show us what you have, and we may be able to help and point out good or bad things we see.

I hope this helps.

John

[SSF156]

Here are photos of the furnace with the wiring diagram.

Also here's a video of it running and me attempting to light it.

Could low propane levels be the reason for it not lighting? Someone said if it isn't level that can cause it not to light.

Video is here https://photos.app.goo.gl/9Y7KFTfPRPHMvjPT8

[JohnB]

Hi,

Your pics and video do help. Your sequence for trying to light the pilot is not entirely correct. In your video, you are doing the steps too quickly.

Originally Posted by SSF156

Here are photos of the furnace with the wiring diagram.

Also here's a video of it running and me attempting to light it.

Could low propane levels be the reason for it not lighting? Someone said if it isn't level that can cause it not to light.

Video is here https://photos.app.goo.gl/9Y7KFTfPRPHMvjPT8

Here is a user manual for that furnace. See page 5 for the pilot lighting instructions. https://www.sunlineclub.com/forums/d...o=file&id=5652

You had the blower running, which is good, as the T stat was turned up high enough to call for heat.

Yes, you turn the red knob to pilot, and you did, then you pressed the ignitor a few times. But I did not see you do the rest of the sequence correctly here.

Ideally, you use two hands to do this, and I understand that to do the video, you had to hold the phone.

Here is what I did not see you doing.

With one hand, and in the pilot position, hold the red knob in, and keep it holding it in. Then push and snap the igniter several times. AND, you have to hold the knob in for at least a minute as the directions on page 5 state. If you let off the red knob too soon, the whole sequence has to start over.

I'll explain what is happening so you can better understand it. The gas valve pilot system has a thermocouple flame-sensing feedback system. This is part of the safety system, so if the pilot ever blows out, it shuts down the gas system. The thermocouple with its copper tube is a feedback system that uses heat to create a small voltage when heated at the sensor's tip.

When you hold the red knob in, a small amount of gas flows to the pilot nozzle/orifice. At this point, gas will only flow when the knob is pressed in. You hit the igniter a few times, which is supposed to light the pilot flame. Once the flame is lit, the flame heat heats the thermocouple tip and sends a signal back to the gas pilot valve that it is OK to keep the pilot flame lit. That signal takes time for the thermocouple to expand from the heat and hold the pilot flame open. If you let go of the red knob too soon, the pilot flame goes out and will never hold the pilot valve open and you have to start all over. If the flame blows out once lit, the thermocouple will sense lack of flame and shut off the pilot as a safety.

The above is what is supposed to happen. In your case, you do not know if the gas flows to the pilot, if the igniter sparks, or if the flame is lit. If the flame does light, does the thermocouple and the gas pilot valve work properly?

So, if you are doing the hold and wait correctly and you still do not know if the pilot is lit, some older furnaces had a peak hole (observation hole) for viewing the pilot and gas burner. I'm not totally sure about yours, as your picture does not zoom in close enough on the gas burner. Some gas systems have a glass sight glass hole you can look through; yours most likely does not, but it may have a teardrop cover that flips open to expose a viewing hole. A small screw holds the tear drop cover, loosen it, swing the cover open, look and see. Then, when all is working, you put the cover back on.

See the red circle on your pic; if you have one, that observation hole would be inside the circle.


Here is a snapshot of where it might be; again, I'm not sure your has it.


As I said before, sometimes the pilot gas line or orifices in the gas valve have crud blocking the gas flow, the pilot valve is not working, the thermocouple no longer works, or the igniter has issues. I'll see if the whole gas valve is even offered for sale anymore and report back later on that.

You asked about the gas pressure. Yes, low gas pressure can make all this worse on a pilot system. The furnace needs an 11" water column (WC) to work properly. This is less than 0.5 psi; it's not a lot. And you do not want a lot above 14" WC, as that creates other issues. Out on the trailer tongue, where the LP tank is, a two-stage gas regulator should set the gas pressure for all the gas appliances in the camper. That regulator could be off setpoint or not working correctly. And yes, the stove burner may light, as even on low gas pressure they can light, but the oven which uses a gas pilot may not work.

I'll caution again and give this friendly advice: Anyone buying a used camper should have the gas system checked for leaks, the appliances checked out, and the main tank regulator ensured to be working correctly before they use it. It's also a good idea to have an annual propane check, or at least one every other year. An LP service or RV tech can perform three checks for you. https://www.sunlineclub.com/forums/f...cks-10981.html

As a side note, RV gas valves are built cheaply and are not serviceable; they just get replaced. RV gas systems do work, but they are not as good as home or commercial gas valves, etc., that can work well for years and years.

On older campers, every time I do an LP gas check, there is a 50/50 chance I will find something not in spec. The main tank regulator goes bad, and the water heater gas valve leaks. On the WH, the gas valve being so close to the outside that it corrodes more easily.

Hope this helps.

John

[JohnB]

I tried to find a "good" clean part number for you on the pilot gas valve. The trial led to superseded and discontinued, and I cannot find a known drop-in replacement.

If you have an HVAC or RV tech who can look at what you have and see if this valve will work, it is the only thing I can find that "might" work. This valve does not include a new thermocouple, but the tech can test your old one with a voltmeter and a grill lighter to heat the tip and see what millivolts they measure.

Again, I don't know if this will replace your valve, but if the RV tech can confirm, it will interchange. I suggest you not order any of this until someone in the know can look at it.

At this point, you are after dealers with old stock on the shelf selling old obsolete parts.

32697 Atwood / Hydroflame Furnace Gas Valve--Hand light pilot only. $189.99 on Ebay https://www.ebay.com/itm/234903607729

32697 Atwood / Hydroflame Furnace Gas Valve--Hand light pilot only $179.99 on Ebay. https://www.ebay.com/itm/126816809409

MC Enterprises MC710-401 Furnace Gas Valve $626.00
https://youngfartsrvparts.com/produc...nace-gas-valve

Atwood/Hydroflame RS401 Valve (32697MC) $797.72
https://www.amazon.ca/Atwood-Hydrofl.../dp/B01DEJQPRU

I doubt they have any warranty, even if they will interchange into your furnace.

For the cost of the gas valve, other parts that may be bad not yet known, and the cost of the RV tech, you may want to look at alternatives.

At the above cost of a gas valve replacement, that may not be all of your issues, if you want the RV furnace, Dometic makes a new replacement for the Atwood 8000 series. I have not checked if Suburban offers something, but Pop Up Camper also uses these smaller furnaces. You will most likely need to modify the side wall of the camper cabinet and the outside air intake and exhaust.

Another option many use, if you are always hooked to shore power in colder weather, is for less than $200, buy a small oil/electric radiator, an approx 1,500 - 1,800 watt version. These look like an old-fashioned cast iron radiator and make almost no noise. The electric heats the oil, then circulates and creates the heat. Or a small ceramic electric heater with tip-over safety protection. In some, the blower oscillates back and forth; they are stationary and blow straight ahead. This type does not have the red hot wires exposed like long ago heaters did. Just make sure you do not overload the electrical in the camper while running a coffee pot, electric griddle, or worse, a hair dryer while the heater is on.

I hope this helps.

John

[SSF156]

I caved in and dropped my TT at a dealer. I am expecting them to tell me it'll cost more to fix it versus replace the entire unit. Any recommendations for newer units that'll replace the 8012 PF?

[JohnB]

Originally Posted by SSF156

I caved in and dropped my TT at a dealer. I am expecting them to tell me it'll cost more to fix it versus replace the entire unit. Any recommendations for newer units that'll replace the 8012 PF?

Hi,

Atwood used to make an updated version of your HF-8012, a ductless direct-discharge furnace. Unfortunately, they sold out to Dometic, and now that Dometic has owned them for a long time, they have redesigned the water heater and the furnaces.

It "appears" they may have discontinued the ductless version of furnaces. They do offer small 12 000 btu furnaces but it looks like they are only ducted heat for inside the camper. You would have to add heat ducts to the camper and enough of them to get the total air flow to overheat the furnace. This may not be that hard, but something to work through. See here for the latest offerings. https://www.dometic.com/en-us/search...vance&count=48

Suburban still makes a small direct interior discharge furnace similar to what you have. https://suburbanrv.com/climate-contr...eries-furnace/

Prices are all over, and then there is free freight or not. The Suburban has a slightly larger output at 16,000 btu but is a direct discharge. They must be popular as many sites are out of stock. But Dyers RV does have 5 in stock. https://www.dyersonline.com/suburban...e-furnace.html

Tax and other modifications to fit the furnace in your space can cost close to $1,000 for parts, not including installation labor.

I hope this helps. Let us know how it turns out. We have others with older campers in the same situation.

John