Furnace short cycling

[WayneM]

We recently purchased a new Keystone Cougar TT, model 22 RBSWE, from camping world in Mesa Arizona. We then headed to the Oregon coast to get out of the high Arizona temperatures and volunteer for the coastal state parks. Being that it is much cooler on the coast in the morning we had the opportunity to use our new Atwood model AFMD 35121 furnace. It is mounted below the refrigerator with a vent on its side plus two other vents, one in the bathroom and one near the end of the bed. When in operation the one that is near the furnace pours out hot air, but the ones in the bathroom and by the end of the bed just radiate some heat, there is no forced air.
The normal operation is for the fan to come on to clear the plenum and enable the safeties, then turn on gas and ignite the burner. During its operation it runs normally and when it reaches it’s set point it shuts down the burner and continues to run the fan purging the plenum area of the furnace. After about 15 seconds or just prior to control board shutting it off it tries to reignite the burner. You can hear the burner ignite for about 2 seconds then stop for about 10 seconds and then try again and again and again until I go up to the in Command control center and shut the furnace off. We currently returned to Mesa and I notified Camping World of this problem and they have scheduled me to have it looked at November 1. They also let slip that there might be an issue from either Keystone or Atwood as to the routing of the duct work or the furnace limit switch.

Anybody else having this problem?

[ctbruce]

Look to make sure all is connected and there are no links in the vent tubing. I'd start there.

[flybouy]

If it's blowing hot air out of one vent then obviously the furnace is working. Kinked/blocked duct hose or hose that's not connected is the only possibility.

[AbHDToyHauler]

Perhaps it shutting down on the high thermal limit rather then the thermostat in trailer being satisfied? If you have plugged line (ducting to rooms) then you are not getting sufficient flow to keep heat exchanger cool enough and the high thermal limit would then be activated? Just something to consider.

[sourdough]

Originally Posted by AbHDToyHauler

Perhaps it shutting down on the high thermal limit rather then the thermostat in trailer being satisfied? If you have plugged line (ducting to rooms) then you are not getting sufficient flow to keep heat exchanger cool enough and the high thermal limit would then be activated? Just something to consider.

^^^With what you have described I would look into this.

[Old Mustanger]

I received a "Service Campaign" (recall notice) from Keystone today where they state that certain Atwood furnace models may have wiring that can come in contact with the exhaust vent tube causing the furnace to shut down in a safe manner The letter states it is for 2018 Alpine 5th wheels but wondering if this could be your problem.

[DocP]

Originally Posted by Old Mustanger

I received a "Service Campaign" (recall notice) from Keystone today where they state that certain Atwood furnace models may have wiring that can come in contact with the exhaust vent tube causing the furnace to shut down in a safe manner The letter states it is for 2018 Alpine 5th wheels but wondering if this could be your problem.

I got the same letter for my 2018 Cougar 32RLI.