Atwood Furnace AFMD30111 Issue

[Griswalds]

Looking for advice from you furnace experts. I had the trailer to the dealer 4 times and it's still happening. The problem - the furnace is cycling off of the limit switch. It runs for 10-12 mins and then the flame shuts off, but the fan remains on. After about 1 min and 30 seconds the flame will reignite. It will do this until it reaches the thermostat temp. The dealer replaced the control board. Still does it.

I decided to do a little troubleshooting. I confirmed it is limiting. With a volt meter across the limit switch, I get 0 volts until the switch opens. Upon which I get 24 volts. I replaced the limit switch just to rule it out and the problem persists. I then started to think maybe it's an air flow issue. Either with the ducting or blower motor. I get good flow from the three floor registers and the one below the shower. I loosened the screws on the external door cover and pulled it away about 1/2 inch. The furnace ran for 45 mins without interruption until it reached the thermostat temp. Tightening the screws causes the furnace to cycle in about 12 mins.

So, does this sound like the blower motor or something else?

Oh yea, the trailer is a 2016 Lacrosse 327RES.

Thx


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[Griswalds]

I fixed it. The flexible ducting from the furnace to the bathroom only needed a length of 5 feet. There was over 12 feet of ducting installed. It was looked like a coiled snake. I removed over 6 feet of the flexible ducting and the furnace ran for over 50 mins continuously until it reached the thermostat temp.


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[* Boondocking *]

Good to hear you got it fixed.

 

[PhoneDude 8289]

I also removed about 8' total of the flex duct in the storage area. Added hard aluminum 3" 90º ells to the furnace taps. Improved airflow considerably to the living area. I did not have the limit cycling problem that I was aware of, just poor to almost no airflow to the living area at the rear of the rv.

 

[MNtraveler]

Wow, good find and good fix!