Furnace Issues

[barnmichael]

I've got a 2006 Cougar 24' fifth wheel. Not sure of furnace model, but it does have a Dometic thermostat for both heating and cooling. There are three wires to the thermostat labeled 12V, COMS, and GND.


My problem is, the furnace comes on and heats the place fairly nicely, then it shuts down. It never comes back on. This morning, with the trailer not used for a month, inside and outside temperature was 39 degrees. I turned on the furnace, set to 78 degrees. The inside temp came up to about 70 degrees and the furnace shut off. When the inside temp dropped to 64 degrees, I turned the thermostat up to 86 degrees. Furnace never came back on. I turned thermostat off, waited 30 seconds then turned back on. Furnace came on, warmed the trailer up to about 74 degrees, then shut off. Through the rest of the day, the furnace would warm it up, then shut off. I had to turn it off, wait a while, then turn it back on. The thermostat is a digital unit with one on/off button that steps through FAN, COOL, HEAT, and OFF. Plus there are up down buttons and a digital temperature display. I do know the thermostat must connect to a control board someplace to control the furnace and the rooftop air conditioner. I do not know where this control board is (furnace or A/C) and nothing is mentioned in any of the documentation that came with the trailer. I don't know if the issue is with the thermostat or with the control circuitry, wherever it is.


Any troubleshooting tips are appreciated.


Michael

[sourdough]

Michael, your problem sounds much like one I had recently. Here is the link:

http://www.keystoneforums.com/forums...ad.php?t=35873

Read the posts. My issue was the thermostat. Your problems sound as if that could be your issue as well. Replaced mine and all is good.

[barnmichael]

Thanks, Danny. My situation is a little different than yours, though. In your case, the burner came on only for a short time, but the fan stayed on all the time. In my rig, when first turned on, the furnace seems to operate normally. It runs until the trailer warms up, then it stops. It puts out plenty of hot air. The burner shuts off and the fan runs for a few minutes, then it stops. Pretty much normal operation. It just never comes on again. The trailer cools down, but the furnace never comes on. I can turn it off and wait until the shut down completes (Using the On/Off button, you cycle through Fan/Cool/Heat/OFF, each with its own LED. When the OFF LED lights, it takes a few seconds to complete the cycle, then the LED goes off.) then step through to Heat again, and the furnace comes on and heats normally. When it gets warm again, it goes off and never comes back on.
The thermostat is still my chief suspect, however. This is our third fifth wheel and we have always had thermostat problems. Our previous trailers had fairly generic thermostats with multiple wires that went to the furnace and A/C respectively. This one only has three wires and digitally communicates with some other board somewhere. That's why I'm questioning the control or the board it is connected to.