Problem Furnace Issue

[J&R-RV]

Hoping for some thoughts on my heating issue:

We have a 39ft 5th wheel with 2 AC units (1 with heat pump - zone 1) and a 2 zone thermostat (Dometic CCC2). The furnace is a Suburban SF-42FQ. This means the on/off furnace control is routed through the zone 1 AC unit.

If I set the furnace on and at a higher than room temp, the blower kicks on and after the delay I hear the gas valve kick in but I don't any burner action. I can't actually hear whether or not the ignitor has sparked. It'll repeat this cycle 3 times without success. The blower stays running until you turn the thermostat back down or off.

If I jumper the thermostat wires (at the furnace) instead of using the controller, the unit fires up. The thing is I continue to hear what sounds like the gas valve kicking in (I think) on a period basis. Not sure if the igniter is sparking at the same time. It seems as though the burner just continues to burn uninterupted.

I would be thinking wiring between the furnace and the AC unit or the AC unit controller board (probably a relay) except for the continuing sound. Thoughts?

I'm thinking of installing another thermostat to control the furnace rather than replacing the AC controller board or rewiring...if one of those are really the issue and assuming it is safe.

I would appreciate any feedback or thoughts.

Many thx - Jack

 

[J&R-RV]

Oh - and I measured the control voltage at 12.5v to 13v (using a dvm). What was curious is that when the valve (?) kicked in I saw the voltage jump. I saw it hit 24v, once 32v and a few times a negative value. Really weird - like perhaps I lost a reference.

Also, I have a full lp tank - although it was filled in 2019.

 

[J&R-RV]

Oh - and I measured the control voltage at 12.5v to 13v (using a dvm). What was curious is that when the valve (?) kicked in I saw the voltage jump. I saw it hit 24v, once 32v and a few times a negative value. Really weird - like perhaps I lost a reference.

Also, I have a full lp tank - although it was filled in 2019.

I fixed it.

The gas line coming off the dual tank regulator has hardly finger tight. It must have been sucking air or messing with the gas pressure when furnace tried starting. As a result, I believe the valve immediately kicked back out due to lack of pressure.

The voltage jumps I saw when the valve kicked in must just be from the initial surge of powering up the valve coil.

I have no idea why 'jumping' out the thermostat would have allow the unit to work in some cases when the thermostat did not. Perhaps my banging around under there was enough to kick it into gear.

Lesson learned - start with the easy stuff first and work toward the more difficult regardless of the simtums.

 

[DemitaD]

We are having similar issue. Furnace kicks on and works for maybe 10-20 min, then it completely stopped working. We had it set at 70, got up at freezing to death at 2 am. It was 64 degrees in the camper. Turned it off and back on, then we hear a click sound every 10 seconds which appears to be coming from the furnace area. ??? So frustrated. We just bought this 4 months ago. It’s a brand new 2021 Sundance Ultra lite by Heartland. Any suggestions

 

[DemitaD]

Oh we have checked propane, connections and all secure. It’s like the ignition switch won’t keep the thing lit?

 

[EricM]

We are having similar issue. Furnace kicks on and works for maybe 10-20 min, then it completely stopped working. We had it set at 70, got up at freezing to death at 2 am. It was 64 degrees in the camper. Turned it off and back on, then we hear a click sound every 10 seconds which appears to be coming from the furnace area. ??? So frustrated. We just bought this 4 months ago. It’s a brand new 2021 Sundance Ultra lite by Heartland. Any suggestions

I have a 2022 Sundance with a similar issue. The furnace will cycle normally for anywhere from 30 minutes to 3 hrs. Then all of a sudden, it won’t restart. I don’t know if you’ve tried this, but the only way I can make mine come back on is to switch the thermostat to fan or ac and let that start up and run for a few seconds, then switch it back to heat. So far, it has come back on every time I’ve done that. I’ve replaced the thermostat already, but that didn’t solve the problem. The last couple of times it stopped working, I would hear the burner re-light while still running. It wouldn’t come back on after that until I cycled the thermostat to fan and back to heat again.