Furnace Problem

[ricere]

The propane furnace in our 2006 KSDP will work perfectly for 24 hours or so and then all of a sudden it will not cut off, and the coach keeps getting hotter and hotter inside until I turn the gas off and pull the 20 amp DC fuse. Turning the thermostat off does no good.

After the unit cools down a bit, I can turn the gas back on, reinstall the fuse, and the unit works perfectly for an undetermined amount of time.

What could be causing the furnace to run out of control periodically? I could take the coach to a service center, but if the problem is not occurring, a technician cannot fix it.

Any advice will be appreciated.

[palehorse89]

Somewhere your thermostat wire is shorted together or make contact with the two wires going to the controller. If the wires are able to make contact it is like the thermostat calling for heat and will not shut down till the wires are seperated. Just a thought. I had it happen to me in my garage heater wire, a staple shorted the two wires together and it would not shut down.

[RVhauler]

agree with palehorse89. Would run a temporary line from furnace to stat or use another stat for shorter wire run and check operation. If your furnace has a electronic board then could also be problem. Can check furnace operations by disconnecting stat wires and replacing with jumper wire on furnace

[Luv2go]

What kind of thermostat do you have, the Comfort Control (most Newmar's have them) or something else? According to the furnace schematic in this manual the only thing that can keep the power going to the gas valve is if the thermostat (which in a Comfort Control is really a relay in the control board in one of your A/C units) stays closed. There also could be an intermittent short in the wiring as has been previously suggested.

Note the Comfort Control does not directly control the furnace, you will only find a phone cord coming out of it and it goes to the A/C unit's control board. The Comfort Control has a micro-controller in it that talks to the control board in the A/C which turns on the relay when the furnace is needed.

To troubleshoot this you can find the blue wires coming out of your furnace (there should be at least one) and unhook it when the problem occurs. If the furnace turns off after a few minutes your problem is in the control board of your A/C unit or wiring, if it does not the problem is in your furnace. This knowledge will help the tech pinpoint the problem even if he can't replicate it.

["007"]

This PDF will show how control is wired to AC's & furnace.

[ricere]

I appreciate you guys taking time to answer my post. Don't think the problem is with wiring because it does not happen consistently. The thermostat works fine with the heat pumps, so I don't believe there is a problem there. The furnace has been working perfectly for the past 36 hours. That makes me believe it is a circuit board problem at the heat pump. That could be an expensive fix.

I have a Comfort Control unit, and thank you all. Luv2go and 007, your advice was very useful.

["007"]

One thing you might want to do is check all the screw connections for your 12 volt wiring.
You will find screw connections in the 12v fuse panel near load center a block on refrigerator deck and even into the control board pins.
Vibration can cause many problems going down the road some of us have been through this.
When I say 12v's that means positive & negative connections you need both with tight connections.
While at control board check all connection pins any one could have a loose connection.
For warmer nights in your future.

[ricere]

Furnace problem fixed. Turned out to be the circuit board in the #1 heat pump (air conditioner). Took it to an RV repair shop, and after some troubleshooting, it was determined that the circuit board was the most logical explanation for the problem. They swapped the circuit board from #2 heat pump to #1 heat pump and the problem is gone.

The circuit boards are identical, but the furnace part on the #2 board is not needed unless there are 2 furnaces installed in the coach. I only have one and it is connected to the #1 heat pump.

Thanks for all the info.

[GaryKD]

Hi ricere,
Thanks for providing the solution. It helps all of us to know that was the final answer.

[Luv2go]

Glad you found the fix and you had a "spare"

["007"]

Thanks for the follow up ricere that information about changing the boards is most helpful if we can remember the next time this comes up.

[ricere]

Hopefully what happened to me will help someone else. That's what it's all about. I appreciate all your feedback.

[Wingman02]

I checked the website tonight to start my search for a furnace issue I am having. Didn't have to search long and got some good information to get me started. Glad yours worked out for you and thanks to those that helped answer ricere's questions!!