Dead furnace
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Forum Name: Podmods, Maintenance, Tips and Tricks
Forum Discription: Ask maintenance questions, share your podmods (modifications) and helpful tips
URL: http://www.rpod-owners.com/forum_posts.asp?TID=4397
Printed Date: 08 Jun 2025 at 4:26am
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Topic: Dead furnace
Posted By: Tars Tarkas
Subject: Dead furnace
Date Posted: 09 Feb 2014 at 9:10pm
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We got to the Smoky Mountains campground at 8pm the other night (just at the end of generator hours). Got set up and turned on the heat. Nothing. The water heater, stove, fridge, all work fine on LP. Nothing at all from the furnace. No fan, no clicks, nada. It worked fine last time I tried it a few weeks ago. Since then, I took the dual tanks off, filled them and put them back. (I'm thinking something like vapor-lock? But as I said, all the other LP appliances work fine.) The fuse is okay. I don't know what else to check. I did check all the frame-grounds I could find and they appear fine. I haven't pulled the furnace, so I don't know if there might be a loose wire from travel vibrations. Of course I took the cover off the thermostat but saw nothing obvious. Is there a way to jump the furnace at the thermostat, or some other way to isolate the problem to the furnace or the thermostat (assuming the problem is in one or the other.) No hookups at the campground, but with the generator in the morning still nothing -- but I could turn on the air con fan by flipping the fan switch to on. It was too cold for the thermostat to allow the air con to come on. I should have tried it after we got the inside warmed up but didn't think to. Fortunately, we were the only people in the campground the net two nights, and the park rangers are essentially non-existent in the campgrounds in winter, so we ran the generator pretty much nonstop and stayed plenty warm with a little 1500 watt heater. TT ------------- 2010 176 FJ Cruiser |
Replies:
Posted By: kymooses
Date Posted: 09 Feb 2014 at 10:17pm
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i would have to think T-stat issue. weird though if you just had it working a while ago. ------------- https://calendar.google.com/calendar?cid=cnBvZC5zcG90dGVyQGdtYWlsLmNvbQ - RPod Rallies https://www.google.com/maps/d/embed?mid=1W1foQXGtrjf8aYly1uh0b-bHPfI&hl=en_US - RPod Owner Map |
Posted By: techntrek
Date Posted: 10 Feb 2014 at 10:26am
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Ditto, especially since the other propane stuff works. I believe if you pull the thermostat you can jump the wires running to the furnace to test it. ------------- Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ http://www.rpod-owners.com/forum_posts.asp?TID=1723 - Pod instruction manual 
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Posted By: P&M
Date Posted: 11 Feb 2014 at 6:02pm
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Awfully cold right now to not have the heater working ... hope you get it up and running quickly ------------- P & M ... and Comet too! 2012 171 -- The Monkey Pod 2018 Ram 2500 |
Posted By: Tars Tarkas
Date Posted: 11 Feb 2014 at 10:15pm
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Thanks for the thoughts... I haven't really fooled with it anymore yet, but I have googled around a bit about the Dometic thermostat. It seems they don't have a stellar reputation. But they aren't very expensive so I guess I'll get another one and give it a try. I'd like to figure out how to bypass the thermostat though to start the furnace just to ensure the problem isn't on that end. Maybe it will become apparent how to do that as I dig in. TT ------------- 2010 176 FJ Cruiser |
Posted By: Outbound
Date Posted: 11 Feb 2014 at 10:33pm
Its quite easy - just short the Rh and W wires - the furnace fan should come on right away. Also, you don't have to replace your thermostat with the stock Dometic model - you can use a household model; the wiring and labelling are identical. Personally, I installed an old programmable thermostat in my R-Pod. ------------- Craig :: 2009 RP171 towed by a 2017 F150 |
Posted By: Tars Tarkas
Date Posted: 11 Feb 2014 at 11:04pm
What is an Rh wire? I see 6 wires, left to right, red, yellow, white, blue, brown, green. Labeled, in the same order, +7.5, Cool, Fur, Hi Fan, Fan, Gnd. W, I suppose is White, Rh might be Red (but that seems odd). I don't know what +7.5 (the red wire) means either. TT ------------- 2010 176 FJ Cruiser |
Posted By: jj
Date Posted: 11 Feb 2014 at 11:49pm
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The following are the wire colors used in a 5 wire thermostat cable. if it is hooked up correctly by installer.
your wiring is as follows from your discription. +7.5 red wire = voltage to thermostate cool yellow = AC fur white wire = furnace hi fan blue wire = high fan speed fan brown wire = normal fan speed grnd green wire = common or ground |
Posted By: jj
Date Posted: 12 Feb 2014 at 12:16am
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http://beamalarm.com/Documents/troubleshooting_rv_furnace_problems.html - Troubleshooting
RV Furnace Problems
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Posted By: furpod
Date Posted: 12 Feb 2014 at 8:55am
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I think you will find that shorting the white and green wires is what you want to try. You said you had ruled out the fuse, so it almost has to be the stat or wireing.. ------------- |
Posted By: CharlieM
Date Posted: 12 Feb 2014 at 11:06am
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I am a bit disadvantaged since I am out camping, but I believe Rh means Red Heat and is +12Volts.White is usually the heater. Green is the heater blower if it has a separate fan control, but POD heaters do not use this function. The heater itself controls the blower. Shorting the green to white may give a false indication of non operation. Normally I would suggest shorting the red to white, expecting to blower to begin its cycle, but then I would remember the FR motto: Let no two Pods be the same. You could check the red wire with a voltmeter to see if is +12V. If it is, try shorting to the white. If the red really measures 7.5V it is some kind of internal logic supply and much more research is required. Replacing the Duo-Therm may be a challenge if you want to retain the two speed A/C fan function. Most house thermostats just have fan on/auto. ------------- Charlie Northern Colorado OLD: 2013 RP-172, 2010 Honda Pilot 3.5L 4WD PRESENT: 2014 Camplite 21RBS, 2013 Supercharged Tacoma 4L V6 4WD |
Posted By: Tars Tarkas
Date Posted: 15 Feb 2014 at 11:44am
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Well, the thermostat works for every thing but the furnace. I've tried shorting it every way that makes any sense at all. The furnace wire to the thermostat ground wire does make a barely audible muffled little click at the furnace, but still no heat or furnace fan. Any other thoughts? Does it seem prudent to replace the thermostat still? TT ------------- 2010 176 FJ Cruiser |
Posted By: techntrek
Date Posted: 15 Feb 2014 at 12:43pm
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Have you checked all of the fuses to make sure the one for the furnace isn't blown? I also just read there is likely a circuit breaker either under the front cover of the furnace or behind the furnace (don't know why it would be back there).
------------- Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ http://www.rpod-owners.com/forum_posts.asp?TID=1723 - Pod instruction manual
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Posted By: Tars Tarkas
Date Posted: 15 Feb 2014 at 1:28pm
The only fuse I know about is the 7.5 amp fuse in the main fuse panel and it's fine. All the fuses there are fine. I have the cover off the furnace, and don't see another fuse. There is a black button thing that I think is hooked straight to the thermocouple. It's pushable but doesn't do anything for me. There is a circuit board at the furnace, mounted sideways, at right angles to the front of the furnace. I can see an off/on switch on there that is on, but without pulling the furnace, I don't see how to access the circuit board. That would mean disconnecting the LP copper pipe, which seems like a last resort to me. And the furnace definitely won't work with no LP, so other than something very obvious like a blown fuse, there's not a lot of point in my pulling the furnace out. If we know there is a fuse there it might be worth it. I'll see what the manual for the furnace says about that. The manual has not been much help so far though. TT ------------- 2010 176 FJ Cruiser |
Posted By: Tars Tarkas
Date Posted: 15 Feb 2014 at 2:16pm
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The furnace itself works! I was able to jump across the relevant connections at the furnace. With the top off of the bench above the furnace it is easy to see where the red and white thermostat wires connect to two light blue wires, one of which has a tape label marked ++++++. This is outside the furnace but under the seat box. The +++++ wire is indeed hot. When I connected those two light blue wires the furnace fan started instantly and the gas lit up in just a few seconds. Disconnecting that jumper caused the flame to go out. The fan ran for about a minute and quit, just as it should. So, early advice/speculation was right on target. I'm totally satisfied now that the problem is in the thermostat or the wires between the thermostat and the furnace, and not with the furnace itself. I'm a little bothered still about the fact that nothing I could short across at the thermostat caused the furnace to start, so I don't know how the wires would have been damaged, but this seems to point to a wiring issue. They are skinny little wires and with the vibrations of normal travel something could have happened. I should be able to check the wires easily enough with an ohm meter though. I'll follow up and let you know how this finally resolves itself, but thanks for the help so far! I know what to do now.... TT ------------- 2010 176 FJ Cruiser |
Posted By: techntrek
Date Posted: 15 Feb 2014 at 4:48pm
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Yup, if jumping those same 2 wires at the thermostat didn't work I agree it is a wiring issue. If you can't easily run new wires to the original thermostat you could mount a dedicated thermostat near the furnace. Just not too close or it will cycle on/off too often and leave the rest of the camper too cold.
------------- Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ http://www.rpod-owners.com/forum_posts.asp?TID=1723 - Pod instruction manual
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Posted By: Boomertype
Date Posted: 15 Feb 2014 at 9:21pm
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Maybe I missed it but did you use a multimeter to check continuty for all the connections to the heater? I never leave home without one.
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Posted By: Tars Tarkas
Date Posted: 22 Feb 2014 at 11:33pm
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The furnace is up and running again. It was a broken thermostat wire. I determined that there was no continuity in the red thermostat wire so I started at the furnace end and pulled a new pair of wires through with the old wire roughly to the thermostat. This is where it gets kind of interesting. The thermostat wires from the furnace do not go to the thermostat. No, they go to the air conditioner. It's a red and white pair that goes from the furnace to the air conditioner, then a 6-wire thermostat cable goes from the air con to the thermostat. You can't check the continuity from the furnace to the thermostat. You can check it from the furnace to the air con and from the air con to the thermostat. The long run with the most bends is the one from the furnace to the air con, so that's what I checked first. For the most part, pulling the wire pair along the existing chase was fairly routine. The cable anchor straps, mostly where the wires turn, were the trouble spots. All of them were doable though, except the one above the ceiling and the lower portion of the air conditioner, where the wire goes from the air conditioner, above the ceiling, over a little then down between the shower stall and the wall outside the shower. I could sort of pull the wire down a little way, so that the end would move up out of the air conditioner, but it would not move at all if I tried to pull it up from the floor, over the ceiling and down into the air conditioner. That's why I pulled from the furnace to about the thermostat. I spliced the new wire to the old wire more or less behind the thermostat. I had to loosen the paneling on the wall with the thermostat to make any of this work. Actually, in hindsight, I guess I could have spliced under the shower if I'd known in advance where the break in the wire was. I did find the wire break. As of now I don't know where it was in the run of wire. I'll see if I can get a good idea when I do the rest of my cleanup tomorrow and put away my tools. It shouldn't be too hard to get a good idea by laying the old wire out along its old path. I was surprised that the thermostat was not directly connected to the furnace. There's bound to be a good reason, but I have no idea what it is. I think you could run a two-wire, dedicated thermostat to the furnace, and that would have been marginally easier, but then I would have had two thermostats (and would have been able to run the air con and the furnace at the same time). None of this overall task was particularly difficult but it would have been much more straight forward if Forest River provided some schematics and better manuals. After carefully reading the manual for the "air handler", I discovered the thing about the furnace wires going to the air conditioner, but I still had no clue whether they went to the inside portion of the air conditioner or the part up on the roof. I took the cover off the roof portion looking for wires that weren't there and I still have to get up there tomorrow to put the cover back on. Thankfully there is no rain in the forecast. TT ------------- 2010 176 FJ Cruiser |
Posted By: Goose
Date Posted: 22 Feb 2014 at 11:51pm
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Sounds like a lot of work, glad that you were able to make the repairs and get the furnace to work as intended. Goose ------------- Mother Goose's Caboose..2011 RP171..07 Grand Cherokee 
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Posted By: yellowstonestu
Date Posted: 23 Feb 2014 at 6:41pm
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I had a hauntingly similar issue last summer with my 173. I had the thermostat replaced, it worked once, then same issue all over again. I took it to my local RV repair place, they couldn't find anything wrong, so finally took the inside cover off the ac unit and found two a loose wire nut there that came from the thermostat. Problem solved?? It worked when I put it away for the cold Colorado winter. Will know more in April when I take it out of winter storage. ------------- Yellowstonestu & Bela the Vizsla 2008 Toyota FJ 2015 RPod 179 (Pod #2) |
Posted By: techntrek
Date Posted: 23 Feb 2014 at 7:55pm
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Glad to hear the problem is solved.
------------- Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ http://www.rpod-owners.com/forum_posts.asp?TID=1723 - Pod instruction manual
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Posted By: sammycamper
Date Posted: 23 Feb 2014 at 9:49pm
Sam ------------- 2012 rPod 173 2008 Trailblazer 4WD V6 |
Posted By: Tars Tarkas
Date Posted: 23 Feb 2014 at 10:33pm
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The job wasn't so hard. Diagnosis was time consuming, mostly because I really didn't know what I was doing. Other than that, pulling a wire was all there was to it. That meant taking off covers, vents, even some paneling, along with the inside cover of the air conditioner. (I did other things that were unnecessary for the job that I did because I didn't know what I was doing.) Then there was the rolling around on the floor and sticking hands and arms in little holes while trying to focus a flashlight on a little brown wire. It terms of the effort involved, there was about as much time and energy involved in my cutting grass. Sam -- Your idea makes sense but it doesn't match the situation. The pod thermostat, mine at least, is like the one at your house. There is a toggle switch on the thermostat to choose Cool, Off, Heat. There are no controls, other than opening and closing manual vents, at the air conditioner or the furnace. I tried, but not too hard, to figure out where the break in the wire was. I think it was in the middle of the chase between under the sink and under the bathroom. That seems very unlikely though, but I still don't know haw the wire would get cut anywhere anyway. I thought a loose wire in a crimp nut or at a ground would have been much more likely. TT ------------- 2010 176 FJ Cruiser |
Posted By: sammycamper
Date Posted: 23 Feb 2014 at 10:52pm
Sam ------------- 2012 rPod 173 2008 Trailblazer 4WD V6 |