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Old 10-18-2018, 07:21 PM   #1
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Furnace runs....for awhile

2016 Thunderbolt XLR 420
Furnace will fire right up. Run and cycle on and off for an hour or 2. Then all of a sudden it shuts off and doesnít even try to come back on no matter how cold it is. If you turn off the T-stat and turn it back on, it fires right up and does the cycle again.
So far, Iíve changed the T-stat and refilled the propane. Still the same prob
em.
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Old 10-18-2018, 07:44 PM   #2
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2016 Thunderbolt XLR 420
Furnace will fire right up. Run and cycle on and off for an hour or 2. Then all of a sudden it shuts off and doesnít even try to come back on no matter how cold it is. If you turn off the T-stat and turn it back on, it fires right up and does the cycle again.
So far, Iíve changed the T-stat and refilled the propane. Still the same prob
em.

It could be one of two things then;

1- The flame is not sufficient to tell the flame sensor not to shut off the gas supply therefore, the system shuts down.

2- Insufficient air flow. If there are enough obstructions in the duct work preventing sufficient air flow, the "sail switch" on the furnace will shut the system down to prevent overheating from hot air not able to exit the furnace.

The furnace system will shut down after 3 attempts to light or stay lit then it will completely shut down as you experienced. When you shut off the thermostat, you restarted that cycle. When it is running, check for air flow at all the floor registers. Also, check any ductwork that may be running into the basement area and/or the underbelly. Check for kinks, radically sharp turns in the ductwork or unnecessary long ductwork with lots of curves/bends.
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Old 10-18-2018, 07:53 PM   #3
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It blows good strong air. When it shut off after reaching the temp set on the thermostat it doesnít even try to restart. At least I canít here it click and I just got a hearing aid and can hear a pin drop at 50í!
To look at any duct work would require a lot of panel removal underneath. But this thing worked a month ago just fine.
I shined a lite in the exhaust and intake and see no obvious obstructions.
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Old 10-19-2018, 10:02 AM   #4
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It blows good strong air. When it shut off after reaching the temp set on the thermostat it doesnít even try to restart. At least I canít here it click and I just got a hearing aid and can hear a pin drop at 50í!
To look at any duct work would require a lot of panel removal underneath. But this thing worked a month ago just fine.
I shined a lite in the exhaust and intake and see no obvious obstructions.

Now with this additional information, it indicates that the furnace works as designed (normally turning on & off) for around 2 hours then shuts down completely. Although it could still be a overheating problem, it could also be a defective control board.
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Old 10-19-2018, 10:08 AM   #5
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Thanks for the info guys. Even to replace the control board I have to pull the furnace. So if I pull it, Iíll replace it. I tried going south so I donít have to use it. That didnít work it was 48 degrees Fahrenheit on the Mexico border a few days ago.
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Old 10-19-2018, 10:12 AM   #6
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Thanks for the info guys. Even to replace the control board I have to pull the furnace. So if I pull it, Iíll replace it. I tried going south so I donít have to use it. That didnít work it was 48 degrees Fahrenheit on the Mexico border a few days ago.

Use electric heaters.....save your propane.
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Old 10-19-2018, 10:19 AM   #7
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Lol....I just bought a small electric heater and I have an electric fireplace that does a pretty good job.
I will survive and
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Old 11-13-2018, 12:24 PM   #8
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It could be one of two things then;



1- The flame is not sufficient to tell the flame sensor not to shut off the gas supply therefore, the system shuts down.



2- Insufficient air flow. If there are enough obstructions in the duct work preventing sufficient air flow, the "sail switch" on the furnace will shut the system down to prevent overheating from hot air not able to exit the furnace.



The furnace system will shut down after 3 attempts to light or stay lit then it will completely shut down as you experienced. When you shut off the thermostat, you restarted that cycle. When it is running, check for air flow at all the floor registers. Also, check any ductwork that may be running into the basement area and/or the underbelly. Check for kinks, radically sharp turns in the ductwork or unnecessary long ductwork with lots of curves/bends.


I too have the very same problem only with an extra twist. As itís running I can hear the unit popping and sputtering when standing outside next to the exhaust. Itís a 2007 Suburban SF-42F propane furnace. It will run for 3p to 45 minutes then shut down. Is there some kind of flame adjustment on them?
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Old 11-13-2018, 12:40 PM   #9
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Do you have the bug screen on your furnace exhaust? One of those holes is air intake for combustion and the other exhaust. Blow some compressed air in just for the heck of it, before you pull the furnace. Seem like the same volume going in as out?
If you have to pull it dont forget to remove the igniter, clean off with wire brush or steel wool, clean the mounting connections( ground) to the burner,especially Important to flame presence function. Other comments on board and sail switch are valid points
Probably a service manual in library section at top of this page!
These are not fun, I did it on a Atwood in a Jayco hand literally had to pull out the kitchen sink to get the furnace out
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Old 11-13-2018, 12:42 PM   #10
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I got mine fixed. A few months ago my thermostat wouldn’t work the A/C. It was to hot so I never tried the furnace. I replaced the thermostat and it worked for the A/C. The new thermostat was a Dometic but a newer model than mine. Yesterday I decided to reinstall the old thermostat and it worked. Furnace worked as it should all night. Not sure what was going on with the old thermostat? Maybe it needed reset? When it quit working I had unplugged the trailer with the A/C running. Next time I went to use it....no go. So maybe unplugging with the A/C running is a nono
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Old 11-15-2018, 10:04 AM   #11
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I have a similar problem the only difference is that my heater will kick back on only if i turn up the temperature or reset. been fighting this for a year now, I took my camper out a couple of weeks ago and the heater work fine the first night than after that it went to manually resetting it or turning up the temp. The one night it did work, it was extremely cold that night. Going to pull out the suburban heater and clean it, hopefully that will fix it otherwise i think it might be the control board.
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Old 11-15-2018, 01:37 PM   #12
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I would start with the thermostat. Mine would restart if I reset it and occasionally it would restart if I turned up the stat. Just make sure you get an exact replacement thermostat. That was one of my problems, the new stat apparently wasn’t the same even though Dometic said it was.
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Old 11-18-2018, 12:19 PM   #13
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As i posted earlier i was having the same issue which is now fixed. This is what i did, not 100% sure which thing fixed it but one these things that i did fixed it. I took the heater out of the camper, used compressed air to blow everything out. Took the back of the fan apart where there was an old mud dauber nest, cleared that out and used my air compressor to blow out the inside. The fin on my sail switch was bent, I straighten that out. I believe it was the bent sail which was the issue. I can provided pictures if you want.
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Old 12-02-2018, 10:03 PM   #14
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I too have the very same problem only with an extra twist. As itís running I can hear the unit popping and sputtering when standing outside next to the exhaust. Itís a 2007 Suburban SF-42F propane furnace. It will run for 3p to 45 minutes then shut down. Is there some kind of flame adjustment on them?


You have the same furnace as I, and I was having the same popping and sputtering problem, and eventually just blew cold air. I disconnected the copper tubing from the furnace and the connection to the bottom of the regulator, blew out the line with my little air compressor. Where did all this oil come from that came gurgling out of the line? Anyway, hooked it back up and now the furnace runs and heats up. However it will still shut down after heating awhile. Guessin I have more than one problem.
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Old 12-03-2018, 09:54 AM   #15
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I think the only way to adjust the flame is to change the nozzle size. From my searching on this, it sounds like your burner is burned out. Meaning it has either rusted or just blown a hole in it.
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Old 12-04-2018, 07:54 PM   #16
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I think the only way to adjust the flame is to change the nozzle size. From my searching on this, it sounds like your burner is burned out. Meaning it has either rusted or just blown a hole in it.


Eureka, I discovered the problem. The oil in propane clogged up my regulator and there was almost no pressure on the outlet side, gas pressure gauge registered only 2 lbs. after replacing the regulator I not only have the best heat Iíve ever had, my 3 burner cook stove has 3 times the output I had previously. Never dawned on me why it took so long to boil a pot of water, now it takes only halve the time. Lesson learned. Pardon me, I have to go turn down the heat, itís getting too hot in here.
Side note: I didnít know propane had oil in it.
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Old 12-04-2018, 07:58 PM   #17
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Thanks for reporting back with your solution!
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Old 12-05-2018, 11:27 AM   #18
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Thanks much for letting us know what you found. It helps a lot, especially when the problem isn't something common.

Propane does contain a little oil from refining, and the odorant they use is Onion Oil, so there's more in that! . It's usually not a problem because it doesn't vaporize with the propane gas, but if the cylinder has ever been turned over or if it's been hooked to a high flow device (think weed burner or high pressure cooker) then it can be carried out of the cylinder.
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Old 12-06-2018, 12:59 PM   #19
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Also I might add that Iíve lived in my 37í triple slide Cedar Creek for 8 years now using propane pretty much every day. Donít imagine it would ever be a problem for part timers and periodic users of RVs. Also the oil never reached the cook stove or the furnace, stayed at the lowest point in the black iron pipe running along the frame. About a 1/3 of a cup came out. Also Iím using the large standup propane cylinder. When time for a refill I carry it on its side in a cradle I built.
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