Furnace woes

[boozedog]

We've got a 2015 FR3 28DS with the suburban propane heater. Is has a funky thermostat that looks like this:



Normally we have the rig connected to shore power and we find that the heat pump and propane furnace work together in conjunction to heat the coach. So far so good.

This past weekend, we tried to use only the furnace (without the heat pump) while boondocking. We turned the thermostat to "heat" mode and set the fan to "auto" and enabled the Furnace mode. We found that no matter how high we turned the setpoint, the furnace would not come on. Ambient temperature was 42 degrees.

To diagnose, we tested the red and white wires coming from the thermostat into the furnace. At all times we got 14V across those two wires, no matter what temperature the thermostat was set. We found that the furnace would start up if we connected the two blue wires from the board together.

Any ideas?

[boozedog]

Also ... does anyone know what make and model of thermostat this is?

[rk06382]

Originally Posted by boozedog

We've got a 2015 FR3 28DS with the suburban propane heater. Is has a funky thermostat that looks like this:

Attachment 187978

Normally we have the rig connected to shore power and we find that the heat pump and propane furnace work together in conjunction to heat the coach. So far so good.

This past weekend, we tried to use only the furnace (without the heat pump) while boondocking. We turned the thermostat to "heat" mode and set the fan to "auto" and enabled the Furnace mode. We found that no matter how high we turned the setpoint, the furnace would not come on. Ambient temperature was 42 degrees.

To diagnose, we tested the red and white wires coming from the thermostat into the furnace. At all times we got 14V across those two wires, no matter what temperature the thermostat was set. We found that the furnace would start up if we connected the two blue wires from the board together.

Any ideas?

I turn off the A/C circuit breaker in the AC panel to prevent heat-pump from running.

[boozedog]

Originally Posted by rk06382

I turn off the A/C circuit breaker in the AC panel to prevent heat-pump from running.

Thanks Robert -- but we were boondocking with the generator off ... so there was no 110V to disable

[Kadiddle]

I have the identical system on my 2015 30DS. Looks like your coach (mine is a 2015.2, second half of model year) has the Atwood A/C/Heat Pump system and the panel you show is from Atwood. The system has the moniker name "AirCommand".

Thought I had the manual for the panel but can't quickly locate. I think it's in my coach and is like one page in the A/C manual. I do know that if you hold down the 'sleep' button for several seconds, the display will tell you what temperature the panel thinks your coach is currently. (Normally the panel shows the set point and I certainly wish it would show the current temperature unless you are changing the set point!!!!! I know what I set it to!!!!!)

I had a short lived problem a couple weeks ago where the panel was showing a much higher current temperature and the furnace would not come on. Problem went away on its own. Not sure related but looking that the panel's sense of the current temperature (via holding sleep) might give you a clue about whether or not the panel is even thinking it should be calling for heat.

BTW, the fan mode does nothing to the propane furnace but rather only the speed of the A/C rooftop unit. But who knows for sure - that panel may care.

Make sure you are turning on the 'Furnace' mode of the panel. The heat pump mode will automatically switch to 'Furnace' when the temperature outside is too low. There's an outside possibility you've set the panel to use the heat pump ('heat' mode without 'furnace'). Without 110V, it may not be automatically switching to propane mode. In mine, pretty sure >>I<< have to push 'Furnace' to get the propane heater to run.

BTW, Atwood was bought by Dometic about two years ago. So getting help might be - blurred.

[boozedog]

Originally Posted by Kadiddle

I have the identical system on my 2015 30DS. Looks like your coach (mine is a 2015.2, second half of model year) has the Atwood A/C/Heat Pump system and the panel you show is from Atwood. The system has the moniker name "AirCommand".

Thought I had the manual for the panel but can't quickly locate. I think it's in my coach and is like one page in the A/C manual. I do know that if you hold down the 'sleep' button for several seconds, the display will tell you what temperature the panel thinks your coach is currently. (Normally the panel shows the set point and I certainly wish it would show the current temperature unless you are changing the set point!!!!! I know what I set it to!!!!!)

I had a short lived problem a couple weeks ago where the panel was showing a much higher current temperature and the furnace would not come on. Problem went away on its own. Not sure related but looking that the panel's sense of the current temperature (via holding sleep) might give you a clue about whether or not the panel is even thinking it should be calling for heat.

BTW, the fan mode does nothing to the propane furnace but rather only the speed of the A/C rooftop unit. But who knows for sure - that panel may care.

Make sure you are turning on the 'Furnace' mode of the panel. The heat pump mode will automatically switch to 'Furnace' when the temperature outside is too low. There's an outside possibility you've set the panel to use the heat pump ('heat' mode without 'furnace'). Without 110V, it may not be automatically switching to propane mode. In mine, pretty sure >>I<< have to push 'Furnace' to get the propane heater to run.

BTW, Atwood was bought by Dometic about two years ago. So getting help might be - blurred.

Thanks Kadiddle that's a great idea ... I will check the ambient reading tomorrow. I can confirm that I did have Furnace mode selected, the little LED next to the furnace button was lit.

[Kentucky Bob]

we had a similar problem. We turned it off and then removed the thermostat from the wall and then replace. Turn it back on and it worked for us.

[Kadiddle]

Note the panel will light the Furnace LED itself if it detects the heat pump won't work at current temperatures. I'm sure you are pushing it but all should note that the LED might be on even though not pushed by user.

[boozedog]

Originally Posted by Kentucky Bob

we had a similar problem. We turned it off and then removed the thermostat from the wall and then replace. Turn it back on and it worked for us.

Thanks Kentucky Bob ... did you disconnect the plug on the thermostat or leave it connected when you removed it from the wall?

[Kentucky Bob]

We disconnected the plug,. It seemed to reset itself after that.

[boozedog]

Tried disconnecting the thermostat and reconnecting, also tried pulling both the furnace and heat pump fuses and replacing. No joy.

Checked ambient temperature on the thermostat, it was showing 74 degrees. But still doesn't seem to call for furnace heat even if I set the setpoint to 85 degrees.

I had Heat mode selected and the furnace button selected (LED was lit) and running only on 12V, no 110V.

Not hearing anything at all from the furnace.

Furnace does start up just fine if I connect the two blue wires from the controller board together.

[Kadiddle]

Sounds like tracing 12VDC wiring to the heater and finding a fuse might be the next step. Also assuming here that you have propane and the valve is open (but then you'd probably hear the furnace trying to light).

[boozedog]

Originally Posted by Kadiddle

Sounds like tracing 12VDC wiring to the heater and finding a fuse might be the next step. Also assuming here that you have propane and the valve is open (but then you'd probably hear the furnace trying to light).

We've confirmed 12V to the heater, the heater does run if we just connect the two blue wires from the control board together.

But for some reason the thermostat doesn't seem to be calling for heat

[dustman_stx]

It's a thermostat issue(either setting isn't correct or it's faulty). The thermostat's job is to connect those 2 wires when heat is needed. If you can manually connect the wires and all is good, then you do not have a furnace issue.

[boozedog]

Originally Posted by dustman_stx

It's a thermostat issue(either setting isn't correct or it's faulty). The thermostat's job is to connect those 2 wires when heat is needed. If you can manually connect the wires and all is good, then you do not have a furnace issue.

Having done some more research, it seems that there are some control boards up in the heat pump that handle the furnace. Right now our theory is that something's gone wrong in one of those control boards or in a connection up there. Received a pretty detailed manual from Atwood, I'm attaching it here in case it's of interest to anyone.

Air Conditioner Service Manual - Rev 11.pdf

[lazbo]

Originally Posted by Kentucky Bob

we had a similar problem. We turned it off and then removed the thermostat from the wall and then replace. Turn it back on and it worked for us.

What thermostat did you get to replace the old one as I am going to replace mine as it comes on once then never comes on again!....thanks in advance!

[lazbo]

Originally Posted by lazbo

What thermostat did you get to replace the old one as I am going to replace mine as it comes on once then never comes on again!....thanks in advance!

Could you send me a picture of the one you replaced it with...thanks in advance

[lazbo]

I am going to replace my thermostat but not sure if I need to replace the control box it came with....have four wires yellow,red,white and black and not sure where they go yellow and white are for the air conditioner I assume and red and black for the furnace...any help would be awesome