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Old 05-21-2019, 03:33 AM   #1
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Furnace runs briefly and then shuts off

Ok team, could use some suggestions. Thor 2018 Super C. Turned on the furnace with the propane tank valve closed by accident. Identified the problem, turned off the furnace (which never lit) and then slowly opened the valve on the tank. Let coach sit 15 minutes hoping to pressurize line. Now it only starts and runs for anywhere from 10- 60 seconds. Turned on the stove and let it run for a while. Been at this for 20 minutes. Super surprised the air would take this long to get out of the line. Any other ideas?
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Old 05-21-2019, 04:08 AM   #2
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Could the furnace control board be wet?
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Old 05-21-2019, 04:18 AM   #3
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Could be. From the outside it is sealed except for the exhaust. It was raining today. You thinking the control board could be wet and causing issues? The exhaust sounds weak if that makes sense. Usually the furnaces in my experience sound robust and pushing a lot of air. This exhaust note seems to stumble
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Old 05-21-2019, 04:25 AM   #4
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it set a hard OFF.
you have to go out and turn off power to the furnace

on the blower wheel there is a procedure based on the flashing light at the brain box right next to the blower




i did it last year by mistake, same thing had propane off . drove me nuts
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Old 05-21-2019, 04:29 AM   #5
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I donít have enough info...
When did you use it last? If itís been 4-6 months you may need to clean out profane.
Have you opened up other propane valves to purge the air? Example...run the refrigerator on propane and the cooktop and/or oven on propane, or the outside BBQ on propane?
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Old 05-21-2019, 04:32 AM   #6
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Thanks. So I should remove the outside panel and read the codes and lastly power it down according to the sticker? Did you have the same issue with the exhaust note sounding off?
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Old 05-21-2019, 04:33 AM   #7
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I used the furnace just a month or so ago. I also ran the stove with no issue for at least half an hour.
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Old 05-21-2019, 02:59 PM   #8
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Not enough information to give a complete diagnosis.

From what you have described it sounds as though your flame circuit could be the issue. If the flame detector does not sense a flame with in 30 or so seconds it shuts the unit down. It will usually attempt this three times before going on lockout.

FWIW
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Old 05-21-2019, 03:31 PM   #9
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I had similar issues
This is the Atwood unit
So I took off the outside panel
Turned off and disconnected propane inlet to furnace
Disconnected all the electrical connectors
Took out the three screws holding the “carburetor”
Then a can of pressurized air and blew everything out several ways and times
Then made sure the spark unit was clean and close to the flame assembly
Then put it all back together
It’s worked ever since
Sometimes it sparks three times and then goes off
But generally by next rotation it started up and worked flawlessly
I generally run it once a month to keep it fresh
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Old 05-21-2019, 04:23 PM   #10
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Originally Posted by CLBeerbower View Post
Could be. From the outside it is sealed except for the exhaust. It was raining today. You thinking the control board could be wet and causing issues? The exhaust sounds weak if that makes sense. Usually the furnaces in my experience sound robust and pushing a lot of air. This exhaust note seems to stumble
Take the outside cover off and check. A common Thor problem even without "air vents". They have a habit of not installing the door gasket correctly and when water gets on or under the control board you get the experience you are having.
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Old 05-21-2019, 10:27 PM   #11
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mine just did the same thing, I did not turn off the gas though. I had been boondocking for 5 nights in two different locations and all was fine. I then drove all day to a new spot. I did go over a high pass approximately 11k feet. Although nothing was running on gas. That night I turned on furnace and it spun up for 30 seconds or so. No flame. tried many times same thing no heat. When I arrived home I took off the outside panel and checked for loose connections. Nothing obvious. I cycled the reset switch by the motor and tried again. 1st attempt tried to light, same on 2nd try, 3rd try it started and worked fine. It seems to be working good now. It had not rained, But it was very windy and blowing dirt. Try the reset switch behind the outside panel.
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Old 05-22-2019, 01:21 AM   #12
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I am fit to be tied. Took off the cover and everything was bone dry. No codes on the small red led. I reset the switch any way and gently wrapped on the small regulator. Same thing. I also called the Thor support line and he thinks it is the circuit board. Ugh. Thinking about calling CW in the morning as Thor said they would
Cover it. Anyone have experience replacing the board? Didn’t look too difficult.
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Old 05-22-2019, 01:46 AM   #13
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Try removing the board and then reinstalling it. I know it sounds crazy but I had a similar issue. I finally did exactly that, removed the board, blew off the connectors (held the board up to the sky and said a prayer) then reinstalled it and it's worked fine ver since!
Now I'm going through a similar situation with my water heater. This did not work this time
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Old 05-22-2019, 11:42 PM   #14
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Replacing the board is very simple, u can't screw it up. Make sure u turn switch off by blower 1st.
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Old 05-23-2019, 12:20 AM   #15
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Thanks all. I replaced the board and I still have the same issue. Bummed.
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Old 05-23-2019, 12:34 AM   #16
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I feel your pain, I am experiencing similar problem.
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Old 05-23-2019, 01:06 AM   #17
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Another data point. We've had a similar issue a couple of times in the in the last year. Bugs, dust - something seems to collect at the ignitor point keeping the system from igniting. My cure has been to use a nozzle on my air compressor and blow air into the system during the ignition sequence. I did a fairly detailed write up if you want to try the fix I used. Here is a link: Furnace won't light - simple fix - updated
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Old 05-24-2019, 08:02 PM   #18
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Quote:
Originally Posted by CLBeerbower View Post
Ok team, could use some suggestions. Thor 2018 Super C. Turned on the furnace with the propane tank valve closed by accident. Identified the problem, turned off the furnace (which never lit) and then slowly opened the valve on the tank. Let coach sit 15 minutes hoping to pressurize line. Now it only starts and runs for anywhere from 10- 60 seconds. Turned on the stove and let it run for a while. Been at this for 20 minutes. Super surprised the air would take this long to get out of the line. Any other ideas?

Well, you say your furnace actually starts and runs (creates heat), but only for 10 to 60 seconds and then shuts off. This is a WAG, but sounds like it might be the over temp limit switch tripping. I expect that when it cools off things work again until the furnace heats up and shuts off again? The time variance may be because the sensor is just flaky.......or perhaps latent heat from repeated re-burns causes earlier shutdowns? Before chocking it up to a flaky sensor it might be worth inspecting the combustion chamber for any partial blockages from ďinsect friendsĒ......to make sure the sensor is not just actually doing its job (not enough air flow through the combustion chamber causing overheating). As I say just a WAG.
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Old 06-01-2019, 10:52 AM   #19
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Is your circuit board mounted horizontally? If so, u need to get the upgrade kit that mounts at about a 45 degree angle. Kťeps the board from getting wet and shorting out.
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Old 06-01-2019, 12:10 PM   #20
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Iíve had the water on the board problem and ended up resealing the furnace cover by installing rubber weather stripping in the slot the cover flange goes into.

Last year I had an issue with the furnace starting, getting a woof of gas igniting and then shutting off. It would go through its three tries and then fail. After some troubleshooting I tracked it down to the gas valve. One of the solenoids was chattering and I donít think it was allowing gas into the burner. I ended up buying a replacement valve and replacing it did the trick. So far no repeat failures. I had to buy the gas valve from a 3rd party. Atwood would not sell me one directly as their lawyers donít want us common folk messing with their stuff, as if the idiot at CW would do any better.
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