2003 Fourwinds E450. Last trip to NY, furnace did fine all day but went to bed and wouldn't hold temperature and could hear blow turn on but ignitor won't fire, so turned it off. Just got it back from RV repair and they said they replaced the circuit board. Checked it before I left and turned on, but as soon as I get home, won't turn on. Kept running thermostat up and down but nothing. Using a digital Honeywell thermostat btw and it's almost new. Can hear the "click" each time I turn off/on so think that's ok. So, turned it off and back on and it fired up again. Got up to 70 degrees, it turned off, and won't come back on to keep temp at 70. I've tried it hooked to house power, batteries and generator....makes no difference. House batteries are at 12.9amp so shouldn't be an issue. Before I lug it back 40 miles to shop, any ideas from the "thinking men" on the board?

I think the board was a bad board, it happens often enough to think that. If the tech thought that was the problem in the first place and he changed it, then it worked when you tried it, then stopped. I would think the new board is a bad board. I bought a Dinosaur board for my last rv and was told they make a more reliable board. It might sound silly, but I carry a spare. It's so easy to plug in a new board and most of the time it solves the problems with furnaces. At least doing that tells me if it in fact is a bad board or not, quick and easy. The only other thing that comes to mind is the your new wall thermostat. I remember people having issues using the auto mode on digital thermostats where it caused malfunctions between the furnace and fan, igniter, and A/C. You would have to google that cause I don't remember the exact problems with that and I cant find my saved info on it.read Old-biscuit and there is a link for more info within this threadhttps://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28593590/print/true.cfm

If your not plugged into shore power then what your experiencing sounds like your battery is getting low. Your heater only generates heat when the fan is running fast enough to open the sail switch (safety mechanism which much be open for the gas to flow) - and when your battery starts to run down the fan may energize but not run fast enough to open the sail switch. Just my 02.

x2 you have a new board ,check out the battery system.

I am in the check the battery camp, but not the 12 volt battery,. Check the battery in the digital t-stat. Even though you say it is a new stat the cheap batteries they sell with anything these days don't last long. And it is a lot easier to check t-stat battery than trailer battery.

VA-Apraisr wrote: I've tried it hooked to house power, batteries and generator....makes no difference. House batteries are at 12.9amp so shouldn't be an issue.The op said his batts are 12.9 volts not amps I assume and it makes no difference. Why would you think its a low battery ? I think the answer is in that link I provided. However, it might be easier to drive the 40 miles and go back to that dealer.

Furnace works; then doesn't; works again? | Good Sam Community

bobndot
Explorer II
Nov 15, 2019
VA-Apraisr wrote:
UPDATE: Furnace worked all week just fine! I did inspect the ducts underneath cabinetry and appears they were shortened to fit more snug and without any kinks. So, most likely the thermostat (and will replace promptly if this ever happens again!) before going to RV mechanic.

"most likely the thermostat" yes, I agree with you, just stick with what you have now...it works .
Sometimes home type digital thermostats can be used and sometimes not.

Well, look at the positive side of all this, think of how much lighter your rv is now that you have shortened your ductwork :B

Glad it all worked out and you had a good time in N.C.
be well,
Bob
Texkoch
Explorer
Nov 14, 2019
My Atwood burner was grounding out the the electrode /spark igniter to the burner. Wish I could copy and pate an image. I took the old burner off and installed a new burner. Two wires and 4 -1/4” nuts. I started to get a sail switch but it works fine. Good luck.
VA-Apraisr
Explorer II
Nov 14, 2019
UPDATE: Furnace worked all week just fine! I did inspect the ducts underneath cabinetry and appears they were shortened to fit more snug and without any kinks. So, most likely the thermostat (and will replace promptly if this ever happens again!) before going to RV mechanic.
Texkoch
Explorer
Nov 14, 2019
My Atwood burner was grounding out the the electrode /spark igniter to the burner. Wish I could copy and pate an image. I took the old burner off and installed a new burner. Two wires and 4 -1/4” nuts. I started to get a sail switch but it works fine. Good luck.
Bordercollie
Explorer
Nov 06, 2019
The furnace in our 2004 Tioga has always worked without problems, but it is comforting when it comes on and cycles properly. There are a lot of DIY videos on You Tube on trouble shooting and fixing furnaces, etc. Finding a good RV furnace repair guy may be difficult.
VA-Apraisr
Explorer II
Nov 06, 2019
Guessing ducts were only slightly kinked since I've never inspected or moved any of them (thinking RV tech was just covering up for the fact that the thermostat was the ONLY issue and they had already installed a new board).
ron_dittmer
Explorer II
Nov 06, 2019
It sounds like you are in good order again. I find it strange that your ducts were kinked. Were they kinked since the rig was new? Or are they in places where your stuff has kinked them.

It seems that your digital thermostat might have been the real culprit. We have the mechanical one shown and love it. I would never get a digital one for the way we use our rig.

At home, we had a digital thermostat for many years and we both cursed it. I finally had a Popeye moment "It's all I can stands, and I can't stands no more". We are back to the old round Honeywell with the coil spring and mercury switch inside.
VA-Apraisr
Explorer II
Nov 05, 2019
Man o man....you guys are a valuable knowledge pool of thoughts!! Yes, I feel it was mainly the Lowe's brand Honeywell not syncing with the RV. But, I've now got a new circuit board, unkinked ducts and new thermostat. Sadly, throw enough money at it and sooner or later a dart will hit the target :) I had better be WARM on that BEACH.
Old-Biscuit
Explorer III
Nov 05, 2019
Sounds like it was the 'thermostat'......

The 'kinked up' ductwork COULD cause issues with air flow (not enough thru the heat exchanger) which would cause overheating and the High Temp Limit Switch would open shutting down gas valve
BUT fan would continue to run....High Temp Limit only stops DC circuit to circuit board NOT DC to Fan.
Fan continues to run cooling down heat exchanger/High Temp Limit Switch Closes ...DC back on circuit board which opens gas vlave/spark electrode fires and re lights because Thermostat Temp Set Point has NOT been reached.

Furnace firing off....reaching t-stat set point and then NOT refiring when temp drops is usually an issue with the thermostat
bobndot
Explorer II
Nov 05, 2019
Thank you for the update, it might have been a combination of the thermostat and that kinked hose. Either way, its good news to hear that it cycled enough times to keep it warm.
Enjoy, N.C.
Bob