Furnace issue

[k81kneal]

We have a 2024 seismic 403 toyhauler. So couple days ago my propane furnace stopped working in middle of night. Assumed it was the propane running out and changed it out. I have a Coleman Mach thermostat. I tried to turn heat on thermostat, heat won’t come on, if I turn dial to change temp even one degree above what the room temp says then screen goes black and won’t come back on unless I turn dial back to below the last temp I just changed it to. So if room was 70 and I turn it to 71 it goes black, can’t see anything on screen so i turn dial back to below the 71 that i changed it to and push knob the screen displays again but heater still won’t come on. I can turn it to anything as long as it’s below the last room temp i turned it to. The cooling system on it works. So playing with it reading online and I did like a reset and pushed knob and held for 12 seconds and then it basically resets, that didn’t work so so did 20seconds for heck of it. That worked, but then the next morning tried using heat and it’s doing samething. Had a tech come over and they switched the main and bedroom thermostat to see if it was a thermostat issue. It wasn’t, whatever thermostat was attached to main wires samething happened. We made sure the little switches behind the thermostat were correct, the little cool/heat/propane switches. We changed out fuse so that’s not the issue, propane is fine. Any thoughts? please help. We have had so many issues with this thing and we bought it brand new.

 

[k81kneal]

Thermostat pics of illuminated and then black.

 

[CBCOCRBO]

We have a 2024 seismic 403 toyhauler. So couple days ago my propane furnace stopped working in middle of night. Assumed it was the propane running out and changed it out. I have a Coleman Mach thermostat. I tried to turn heat on thermostat, heat won’t come on, if I turn dial to change temp even one degree above what the room temp says then screen goes black and won’t come back on unless I turn dial back to below the last temp I just changed it to. So if room was 70 and I turn it to 71 it goes black, can’t see anything on screen so i turn dial back to below the 71 that i changed it to and push knob the screen displays again but heater still won’t come on. I can turn it to anything as long as it’s below the last room temp i turned it to. The cooling system on it works. So playing with it reading online and I did like a reset and pushed knob and held for 12 seconds and then it basically resets, that didn’t work so so did 20seconds for heck of it. That worked, but then the next morning tried using heat and it’s doing samething. Had a tech come over and they switched the main and bedroom thermostat to see if it was a thermostat issue. It wasn’t, whatever thermostat was attached to main wires samething happened. We made sure the little switches behind the thermostat were correct, the little cool/heat/propane switches. We changed out fuse so that’s not the issue, propane is fine. Any thoughts? please help. We have had so many issues with this thing and we bought it brand new.

Hi. I dont know your furnace usage habits but my first guess would be that the sail switch in the furnace box has a build up of dust and needs cleaning. Our last RV( A 2020 Jayco 29 RKS) had to be serviced three times over the four years we used it. Each time the furnace had to be removed and blown clean. The last time we replaced the sail switch for a new one. Not a big or expensive job but damned inconvenient. And our RV was permanently placed at a seasonal site. We now have a new 2025 but got a seven year warranty package.
Cheers
Rick

 

[k81kneal]

Hi. I dont know your furnace usage habits but my first guess would be that the sail switch in the furnace box has a build up of dust and needs cleaning. Our last RV( A 2020 Jayco 29 RKS) had to be serviced three times over the four years we used it. Each time the furnace had to be removed and blown clean. The last time we replaced the sail switch for a new one. Not a big or expensive job but damned inconvenient. And our RV was permanently placed at a seasonal site. We now have a new 2025 but got a seven year warranty package.
Cheers
Rick

So had a tech look at it. he did a reset on the furnace itself. It got the blower to start working and the heat to work for like 15-20 seconds then the light goes out and blower will continue for like couple mins then blower will shut off. Then blower will come back on like 15 mins later but no heat and it will just keep going that with the blower without the heat. He is telling me the pilot light is basically not staying lit. I can then turn it off then on and same will happen. He thinks it’s the control board but can’t get to it because need to break the gas line which he is not authorized to do in our state so waiting on another tech who is authorized to deal with the gas line. It’s how the furnace is set up, the control board is behind the furnace which has to be pulled out. So waiting on new tech.

 

[Rodgerhassard]

When the high limit on the furnace opens will take out the stat and leave the blower running.

To check, bypass the the high limit, and the test it again. The furnace should fire normally. Just make sure you don't let it run for very long or it will overheat.

Then install a high limit.

 

[Old_Salty]

We have a 2024 Seismic.

We had a similar problem where the furnace would work for a short period and then shut off. The furnace would not re-ignite until the furnace was allowed to cool, was shut off and then back on - resetting the safety devices. It turns out the high limit was shutting the furnace down - as it should.

What was found was one of the duct connections to the furnace had disconnected and allowed the hot air to immediately return to the furnace inlet side and therefor, the plenum would overheat. Repair was simple, reconnect the duct properly to the furnace. The duct connections are pretty crappy and are a fairly loose twist fit. I tightened the duct headers by bending the retaining flap to more securely hold the headers and used aluminum duct tape to better secure the duct headers to the furnace plenum. This solved our issue.

This was very aggravating and took longer to isolate than it did to repair. I did the work myself. Good luck!

 

[k81kneal]

Thank you for your reply. We were able to get a tech out and they replaced the control board. They said it’s a common issue. Good thing i’m still under warranty.

 

[Old_Salty]

Great to hear your furnace is repaired!