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Old 01-18-2022, 10:04 PM   #1
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THOR #10644
Furnace makes weird repeated relay(?) noise and isn't even on?

2016 Thor Outlaw Class-A 37RB
I'm looking to see what furnace model is installed in it...

It's been fine all along. Today it rained for the first time in weeks.
After about an hour of light rain, the furnace starts making a click/rev click/rev click/rev sound over and over. This does not sound like the 'snap' of an igniter! More like a relay clicking, a motor revving for not even a second and then cycle repeats. The cycle will repeat two or three times per second and not stop even after a full minute or more!

All this happens and I'm not even calling for heat!
I can't find a way to stop this from happening - except to actually call for heat!
When I set the thermostat to something like 80 to trigger heat, the clicking stops, the fan starts up, the propane burner kicks in and all seems ok.
IF I just let it run that way, eventually the furnace will heat to 80 and turn off. No clicking...
BUT, if I go to the thermostat and either turn it off or even turn down the temp so it won't kick on, the click starts right up!

Yes, I've read that wet controller board is a likely cause. Does this just dry out and resolve? Anything I can do?

Finally, the big question is how do I disable the furnace from even getting any power? There's no 12v fuse that I can see. Even the "Store" switch won't shut it down. I suspect that is because I'm sitting on shore power?
I'd like to stay on shore power and disable the furnace completely? Where is it connected?? ...Freakin' Thors!...

BTW - my furnace is under the three burner stove and oven, so access from inside is not really intended. Unless maybe that stove unit comes out of there??

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Old 01-18-2022, 10:14 PM   #2
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You should have a fuse somewhere.
Is there a service door outside or just the vent pipe.
If no door, in your fuse panel there is a circuit breaker, flip it.
Hope this helps.
Terry
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Old 01-18-2022, 11:55 PM   #3
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Seen this happened before. Your circuit board has gotten wet.
Open outside access and dry the board with a hairdryer.
That worked on a forest river trailer.
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Old 01-19-2022, 02:10 AM   #4
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Yep, wet board that MAY dry out on its own.

You have 2 ways to kill the furnace:

1 - Remove the "APPLIANCE" fuse. This will also likely kill your water heater and absorption fridge.
2 - Remove the outside cover, find the "reset" switch near the circuit board and switch it to the RESET/OFF position.



In either method you will lose power to the thermostat and control power for the Air Conditioner.
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Old 01-19-2022, 03:26 AM   #5
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THOR #10644
I stopped looking for the fuse. It's definitely not in the 12V Coach fuse panel. It won't be a 120v breaker because the furnace is 12v and everything else (fridge, hot water heater, microwave) is 120 and marked in the breaker panel individually.

Tomorrow I'll even look inside the chassis fuse panel, even though that's a stretch.
I can also pull the coach 12v master fuse and see what happens..

Eventually, the furnace was running normally and kicked off. No repeating noise. I waited several minutes and turned the heat off at the tstat. It's been quiet since. I'll try to pick up the trail again tomorrow.

Thanks for the help!
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Old 01-19-2022, 04:23 AM   #6
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Quote:
Originally Posted by lmichel View Post
I stopped looking for the fuse. It's definitely not in the 12V Coach fuse panel. It won't be a 120v breaker because the furnace is 12v and everything else (fridge, hot water heater, microwave) is 120 and marked in the breaker panel individually.

Tomorrow I'll even look inside the chassis fuse panel, even though that's a stretch.
I can also pull the coach 12v master fuse and see what happens..

Eventually, the furnace was running normally and kicked off. No repeating noise. I waited several minutes and turned the heat off at the tstat. It's been quiet since. I'll try to pick up the trail again tomorrow.

Thanks for the help!
Don't bother looking for it in the chassis fuse panel - it isn't there.

I don't know what you call the "12v master fuse" - no such thing.

Read post #4 for the fuse that provides 12 VDC control power to you appliances, including the furnace.
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Old 01-19-2022, 06:15 PM   #7
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THOR #10644
Furnace Weird noise (Wet Board?) UPDATE

Quote:
Originally Posted by 16ACE27 View Post
Yep, wet board that MAY dry out on its own.

You have 2 ways to kill the furnace:

1 - Remove the "APPLIANCE" fuse. This will also likely kill your water heater and absorption fridge.
2 - Remove the outside cover, find the "reset" switch near the circuit board and switch it to the RESET/OFF position.



In either method you will lose power to the thermostat and control power for the Air Conditioner.
Now that it has stopped raining and there's plenty of daylight I got back to exploring this issue.
Before I did anything at all, I turned the heat back on at the TSTAT.
Now, the furnace blower spins up and after the proper amount of time, the burner kicks on and only stays on for a few seconds. The blower continues to run. Eventually, the burner comes back on briefly and goes back out. The amount of time that the burner stays on is not the same every time.
I turned the heat off at the TSTAT.
When I went outside to pull the cover - to my amazement, none of the screws were installed to hold the cover on. Only the two screws to hold the vent in place! Mind you, I bought this RV brand new! No one that I am aware of has ever been inside the furnace.
Pulling the cover, I turned the heat back on and went out to watch.
There really was nothing to see.
The same symptom. I turned off the reset switch. I carefully pulled the sail switch and noticed it didn't have that distinctive microswitch click when moving the long aluminum 'sail' arm. I put a meter on it and it certainly worked fine when testing by moving the arm back and forth.
I hooked it back up but not installed so I could move the arm by hand while it was running. By doing this, I couldn't even make the burner try.
Now I reinstalled it back the way it was and tried again. Back to the same symptom.
I also inspected the LED on the board - there were no flashes, messages, etc.. The LED was not lit at any point while I investigated.
It's now all put back together - this time with screws for the cover!
One thought I had was the propane amount. My tank is only a third full and has never been so empty. Propane pressure??
However, my stove burners and hot water burner both work fine.
The model is a AFMD35141_A Atwood/Dometic
Finally, I did find the "Appliances" 12v fuse. I have no idea how I missed that the first time

Ideas?

PS - I'll be topping off my propane - but not until Monday at the earliest.
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Old 01-19-2022, 06:45 PM   #8
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THOR #7035
Quote:
Originally Posted by lmichel View Post
Now that it has stopped raining and there's plenty of daylight I got back to exploring this issue.
Before I did anything at all, I turned the heat back on at the TSTAT.
Now, the furnace blower spins up and after the proper amount of time, the burner kicks on and only stays on for a few seconds. The blower continues to run. Eventually, the burner comes back on briefly and goes back out. The amount of time that the burner stays on is not the same every time.
I turned the heat off at the TSTAT.
When I went outside to pull the cover - to my amazement, none of the screws were installed to hold the cover on. Only the two screws to hold the vent in place! Mind you, I bought this RV brand new! No one that I am aware of has ever been inside the furnace.
Pulling the cover, I turned the heat back on and went out to watch.
There really was nothing to see.
The same symptom. I turned off the reset switch. I carefully pulled the sail switch and noticed it didn't have that distinctive microswitch click when moving the long aluminum 'sail' arm. I put a meter on it and it certainly worked fine when testing by moving the arm back and forth.
I hooked it back up but not installed so I could move the arm by hand while it was running. By doing this, I couldn't even make the burner try.
Now I reinstalled it back the way it was and tried again. Back to the same symptom.
I also inspected the LED on the board - there were no flashes, messages, etc.. The LED was not lit at any point while I investigated.
It's now all put back together - this time with screws for the cover!
One thought I had was the propane amount. My tank is only a third full and has never been so empty. Propane pressure??
However, my stove burners and hot water burner both work fine.
The model is a AFMD35141_A Atwood/Dometic
Finally, I did find the "Appliances" 12v fuse. I have no idea how I missed that the first time

Ideas?

PS - I'll be topping off my propane - but not until Monday at the earliest.
If the stove and the water heater work, it's not the propane system. It may be the furnace solenoid operated propane valve but most likely corrosion has set in on the furnace control board. You may be able to revive it by pulling it out and cleaning with alcohol.

If you do end up replacing the control board I highly recommend the Dinosaur replacement:

https://www.amazon.com/gp/product/B009XU7H8Q/
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Old 01-19-2022, 08:21 PM   #9
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Quote:
Originally Posted by 16ACE27 View Post

If you do end up replacing the control board I highly recommend the Dinosaur replacement:

https://www.amazon.com/gp/product/B009XU7H8Q/
Hmmmm... Regardless, this sounds like a good spare to have stored away
I should probably look up the same type of board for my hot water heater - and an element too!
I should probably ask: do you have recommendations for those parts as well? My hot water heater is a GC6AA-10E. Dual 110AC/LP
The Hot Water Heater is working fine, but the element is still the original (2016) so I know I'm due ;-)
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Old 01-19-2022, 10:11 PM   #10
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THOR #7035
Quote:
Originally Posted by lmichel View Post
Hmmmm... Regardless, this sounds like a good spare to have stored away
I should probably look up the same type of board for my hot water heater - and an element too!
I should probably ask: do you have recommendations for those parts as well? My hot water heater is a GC6AA-10E. Dual 110AC/LP
The Hot Water Heater is working fine, but the element is still the original (2016) so I know I'm due ;-)
The Dinosaur replacement board for you water heater is probably:
https://www.amazon.com/gp/product/B0130Y8I1K

No clue on the 120 VAC element but they all have the same fit and connections. Probably one from your local big box store would work.

https://www.lowes.com/pd/Utilitech-W...lement/3692734

$8 at Lowes.
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Old 01-20-2022, 08:08 PM   #11
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Check your gap at the igniter,
Check the ceramic cover on igniter.
Check the burner head.
You need the igniter to be gapped 1/8” from burner head for the gas solenoid to see ground to work. I use a 1/8 allen wrench sideways to check.
Terry
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Old 01-21-2022, 05:04 PM   #12
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THOR #10644
RESOLVED: Furnace makes weird repeated relay(?) noise..

I pulled the board and gave it a really close inspection. No signs of corrosion, no condensation on components, etc..
I put the board in a plastic zip-loc with a couple desiccant packs from past shipping boxes overnight.

Reinstalled board - Good to Go!

I have ordered the Dinosaur Spare and also the similar spare they make for my Hot Water Heater. Having those will certainly help me sleep better at night

Thanks so much for all your help and suggestions.
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Old 01-21-2022, 06:50 PM   #13
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Great job, glad you fixed it.
Terry
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Old 01-22-2022, 12:18 PM   #14
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I have a Dometic model 35151 with some of the same symptoms you describe, sometimes runs fine, sometimes won't fire at all, sometimes burner kicks in and out multiple times during a single cycle. I did much of the same things you did, the one that has worked for a couple of (cold) days so far was to pull the circuit board out, remove and re connect wires, gently wiggle all wires and then reinstall the circuit board. (it was not wet or sitting in water) Once I get to a warmer place than northern Florida I plan to pull the burner and clean,check/gap electrodes and inspect and reconnect every wire and connector I can find. I already have a spare sail switch on hand and may buy a spare circuit board to have on hand if it is not too many $$$.
-Ken
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Old 01-26-2022, 08:55 PM   #15
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Quote:
Originally Posted by lmichel View Post
Now that it has stopped raining and there's plenty of daylight I got back to exploring this issue.
Before I did anything at all, I turned the heat back on at the TSTAT.
Now, the furnace blower spins up and after the proper amount of time, the burner kicks on and only stays on for a few seconds. The blower continues to run. Eventually, the burner comes back on briefly and goes back out. The amount of time that the burner stays on is not the same every time.
I turned the heat off at the TSTAT.
When I went outside to pull the cover - to my amazement, none of the screws were installed to hold the cover on. Only the two screws to hold the vent in place! Mind you, I bought this RV brand new! No one that I am aware of has ever been inside the furnace.
Pulling the cover, I turned the heat back on and went out to watch.
There really was nothing to see.
The same symptom. I turned off the reset switch. I carefully pulled the sail switch and noticed it didn't have that distinctive microswitch click when moving the long aluminum 'sail' arm. I put a meter on it and it certainly worked fine when testing by moving the arm back and forth.
I hooked it back up but not installed so I could move the arm by hand while it was running. By doing this, I couldn't even make the burner try.
Now I reinstalled it back the way it was and tried again. Back to the same symptom.
I also inspected the LED on the board - there were no flashes, messages, etc.. The LED was not lit at any point while I investigated.
It's now all put back together - this time with screws for the cover!
One thought I had was the propane amount. My tank is only a third full and has never been so empty. Propane pressure??
However, my stove burners and hot water burner both work fine.
The model is a AFMD35141_A Atwood/Dometic
Finally, I did find the "Appliances" 12v fuse. I have no idea how I missed that the first time

Ideas?

PS - I'll be topping off my propane - but not until Monday at the earliest.
If you were missing access panel screws then moisture got to your board.
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Old 01-28-2022, 03:55 PM   #16
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Quote:
Originally Posted by lmichel View Post
2016 Thor Outlaw Class-A 37RB
I'm looking to see what furnace model is installed in it...

It's been fine all along. Today it rained for the first time in weeks.
After about an hour of light rain, the furnace starts making a click/rev click/rev click/rev sound over and over. This does not sound like the 'snap' of an igniter! More like a relay clicking, a motor revving for not even a second and then cycle repeats. The cycle will repeat two or three times per second and not stop even after a full minute or more!

All this happens and I'm not even calling for heat!
I can't find a way to stop this from happening - except to actually call for heat!
When I set the thermostat to something like 80 to trigger heat, the clicking stops, the fan starts up, the propane burner kicks in and all seems ok.
IF I just let it run that way, eventually the furnace will heat to 80 and turn off. No clicking...
BUT, if I go to the thermostat and either turn it off or even turn down the temp so it won't kick on, the click starts right up!

Yes, I've read that wet controller board is a likely cause. Does this just dry out and resolve? Anything I can do?

Finally, the big question is how do I disable the furnace from even getting any power? There's no 12v fuse that I can see. Even the "Store" switch won't shut it down. I suspect that is because I'm sitting on shore power?
I'd like to stay on shore power and disable the furnace completely? Where is it connected?? ...Freakin' Thors!...

BTW - my furnace is under the three burner stove and oven, so access from inside is not really intended. Unless maybe that stove unit comes out of there??
See your electrical wiring diagrams for the furnace and air conditioner. The furnace is controlled/wired from a circuit board in the air conditioner.
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Old 01-28-2022, 04:14 PM   #17
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Originally Posted by Junodtim View Post
See your electrical wiring diagrams for the furnace and air conditioner. The furnace is controlled/wired from a circuit board in the air conditioner.
Nope, that's backwards. the thermostat (and hence the A/C control power) is fed from the 12 VDC coming from the furnace.
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Old 01-28-2022, 04:20 PM   #18
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If your board works again after drying get some Conformal Coating for circuit boards and that should protect it from the weather.
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Old 01-28-2022, 07:16 PM   #19
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Originally Posted by Galobo View Post
If your board works again after drying get some Conformal Coating for circuit boards and that should protect it from the weather.
If you want to go to that length, please clean it good with a brush and alcohol first so as to not seal in any corrosion.
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Old 01-28-2022, 09:07 PM   #20
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If you want to go to that length, please clean it good with a brush and alcohol first so as to not seal in any corrosion.
For sure 👍
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