AC and furnace?

[96-vetteman]

Had an interesting thing happen this morning. We are out rv-ing and selected the furnace option in our 2013 XL 378TS and our AC unit came on. The furnace also ran but didn't put out any heat. I don't believe the two systems are in any way connected other than by the thermostat. Could it be a bad stat or a wiring issue, worked great last time we were out. Has anyone had the same issue? I would like to hear from anyone on this subject. Thanks in advance.

[Falcon35]

If you set your thermostat fan for anything except auto it will start the ac fan when the furnace come on. If the furnace is not putting out heat, check that it is getting propane. Turn it on and go outside and listen for a sparking sound. If you hear that and the furnace doesn't light then I would light a burner on the stove to make sure the LP is flowing. You may have to try the furnace several times before it lights if you have not used for sometime.

[96-vetteman]

We have a Dometic thermostat. It has a auto setting with the fan mode(was set to high not auto when furnace and AC came on together). The stat has the following selections: fan/cool/furnace with a on/off button on the bottom. The AC works fine by it's self. Just can't figure out why they both come on together when the furnace mode was selected. News flash.....just selected auto in fan mode. AC does not come on. Thanks for the info.

[OldCoot]

What Falcon35 said, fan has to be on "Auto"

[Falcon35]

On mine if the thermostat fan setting is anything but auto the AC fan will come on when I select furnace. Before you turn the furnace on set the fan to auto.

[Flybob]

The first time the furnace is run, it may take a few times to get gas to it to light. After a few failed tries, it will go into safety shutdown and not try again until you reset it by shutting it off. Wait a few minutes. Then set thermostat to AUTO ( not high or low) and try again. As mentioned, you should hear the furnace lighter clicking (outside near furnace door). The fan should come on as soon as it calls for heat after a short run, the furnace should try to light. If this is the first time running the furnace or first time in a while it may take a few tries.