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Old 10-25-2021, 04:32 AM   #1
Brantel
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Join Date: Oct 2020
Location: Newport
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Furnance issues

Tried to use our furnace for the first time this fall. It worked fine back in the early spring. This unit might have an hour of total run time since new.

Symptoms:

When cold the furnace fan comes on
Purge cycle completes
Ignition and flame starts
Heat is being produced
After it warms up, it shuts down with a one flash code (limit switch/airflow fault)
Main board has a buzzing relay until I cycle power to unit.


I have checked the vents and they are all open. The inside of the furnace is spotless. The burner is clean, the ignitor rod is clean, the combustion chamber/tube is clean and the external intake/exhaust is clean. Fain squirrel cage is clean and fan runs up to full speed.

Fan produces normal airflow.
Sail switch is obviously OK or it would never call for ignition.
Ignition and Ignitor are obviously OK or it would not ever ignite.
Propane is OK as it runs unit it warms up then quits. Stove, oven, water heater, etc. work fine.

I have ordered another thermal high limit switch but understand that these rarely fail.

What concerns me is the buzzing relay sound after the unit shuts down in error.

Any ideas other than change the high temp limit switch?
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2021 Keystone Cougar Half-Ton 32BHS 5th Wheel
2022 F-450SD, Lariat Ultimate, CC, 4WD, FX4, Rapid Red, Curt A16/R24 Slider
Upgraded: 2020 F-250SD, XLT Pre, CC, SWB, 4WD, FX4, HCTP, 6.7 PSD, 3.55 e-lock, Blue Jeans Metallic
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Old 10-25-2021, 04:38 AM   #2
ChuckS
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bad control board may also be in play.. the relay shouldnt buzz...
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Old 10-25-2021, 05:00 AM   #3
Brantel
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bad control board may also be in play.. the relay shouldnt buzz...
I agree. I am starting with the cheap stuff first LOL.
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2021 Keystone Cougar Half-Ton 32BHS 5th Wheel
2022 F-450SD, Lariat Ultimate, CC, 4WD, FX4, Rapid Red, Curt A16/R24 Slider
Upgraded: 2020 F-250SD, XLT Pre, CC, SWB, 4WD, FX4, HCTP, 6.7 PSD, 3.55 e-lock, Blue Jeans Metallic
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Old 10-25-2021, 09:21 AM   #4
JRTJH
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A 2021 Cougar Half Ton furnace is warrantied by the furnace manufacturer for at least 2 years. There is no need to take the trailer to a "RV dealer" for service on the furnace. Use your furnace owner's manual (Atwood or Suburban) to locate a service center near you and contact them. Usually relying on a RV dealership to service the furnace results in weeks or months of delay to get an appointment. The manufacturer's service facilities (some of which are RV centers) usually include private businesses that can service/repair your furnace without relying on the "often booked RV dealer".....

There's no need for you to be "buying parts to throw at a new furnace"... Let the furnace manufacturer do that expensive stuff.....
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Old 10-25-2021, 10:09 AM   #5
Brantel
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Quote:
Originally Posted by JRTJH View Post
A 2021 Cougar Half Ton furnace is warrantied by the furnace manufacturer for at least 2 years. There is no need to take the trailer to a "RV dealer" for service on the furnace. Use your furnace owner's manual (Atwood or Suburban) to locate a service center near you and contact them. Usually relying on a RV dealership to service the furnace results in weeks or months of delay to get an appointment. The manufacturer's service facilities (some of which are RV centers) usually include private businesses that can service/repair your furnace without relying on the "often booked RV dealer".....

There's no need for you to be "buying parts to throw at a new furnace"... Let the furnace manufacturer do that expensive stuff.....
Yeah, unfortunately there are no Dometic service centers around me that I can find other than RV dealers.

I am not waiting on a dealer to fix this. I use my RV and refuse to own something that sits at a dealer for most of its life. If it cost me a couple hundred bucks oh well that is RV ownership for you.
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2022 F-450SD, Lariat Ultimate, CC, 4WD, FX4, Rapid Red, Curt A16/R24 Slider
Upgraded: 2020 F-250SD, XLT Pre, CC, SWB, 4WD, FX4, HCTP, 6.7 PSD, 3.55 e-lock, Blue Jeans Metallic
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Old 10-25-2021, 10:28 AM   #6
sourdough
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Brian from the sound of things it sounds a lot like the symptoms when one of mine failed. It was the control board. I don't know what they cost in this day and time but seems like $100 - $120?? Been a few years back but I agree, if they are that price it beats leaving it at a dealer for them to abuse for 6 mos., and it was easy to change out as well.
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Old 11-02-2021, 05:36 AM   #7
Brantel
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So I wanted to follow up to this thread to inform the group of the root cause of this issue.

Turns out it was the crappy cheap plastic self resetting circuit breaker that Keystone used for the furnace.

The breaker was not tripping but it was overheating and then just putting out enough voltage to cause the furnace to instantly stop (which is not a great way to shutdown since it does not allow for cool down) and the main control board relay's to buzz or chatter.

I found a video on Youtube where the guy had the exact same issue and the exact same weird sound from the control board.



My lesson learned is do not assume the power is OK. Get a meter and check it while under load in operation and monitor till the fault occurs no matter how inconvenient it is to do so.


Safety note: Everyone should pull their furnace out and clean all the sawdust and other wood particles/construction crap out of the area where the furnace is mounted. If yours looks like mine, it is a miracle it has not already caught fire!
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2022 F-450SD, Lariat Ultimate, CC, 4WD, FX4, Rapid Red, Curt A16/R24 Slider
Upgraded: 2020 F-250SD, XLT Pre, CC, SWB, 4WD, FX4, HCTP, 6.7 PSD, 3.55 e-lock, Blue Jeans Metallic
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