Furnace won't work

[04fxsts]

We keep our winterized 2015 ACE next to the garage here at home so it is right there if needed. Our home is all electric so if we would loose power we have no heat or anything else. Went out a few days before the bug winter storm to make sure everything, especially the furnace was working. Well it was not, would try to fire three times and then shut down. From reading here I guessed it was the control board so removed it. The bottom was coated with a layer of ice so that convinced me to replace it.
Got a replacement from Dinasaur Electronics so all good I thought. Put in and nothing happens, put in the old board and nothing. Called DE and they went through troubleshooting with me and found the thermostat to be bad which makes sense. It is an analog AC/heat Coleman Mack https://www.rvpartscountry.com/Colem...hermostat.html I tried to post a picture but couldn't.
I can replace with the same thing but thought I would ask if anyone recommends another thermostat near the same price range or tips on the actual change out. Thanks, Jim.

[Jimbo56]

I replaced mine with the digital version of the Coleman Mach 3. Easy diy install.
The digital has a much closer range and keeps the unit at more consistent temps also.

But I have to ask, did you bleed the air out of your propane lines before trying the furnace? If you hear it trying to light, I would think the thermostat is calling for heat and working properly. Assuming you bled the air out, there are other threads on this forum that discuss a “sail” switch being bad.

[16ACE27]

Originally Posted by 04fxsts

We keep our winterized 2015 ACE next to the garage here at home so it is right there if needed. Our home is all electric so if we would loose power we have no heat or anything else. Went out a few days before the bug winter storm to make sure everything, especially the furnace was working. Well it was not, would try to fire three times and then shut down. From reading here I guessed it was the control board so removed it. The bottom was coated with a layer of ice so that convinced me to replace it.
Got a replacement from Dinasaur Electronics so all good I thought. Put in and nothing happens, put in the old board and nothing. Called DE and they went through troubleshooting with me and found the thermostat to be bad which makes sense. It is an analog AC/heat Coleman Mack https://www.rvpartscountry.com/Colem...hermostat.html I tried to post a picture but couldn't.
I can replace with the same thing but thought I would ask if anyone recommends another thermostat near the same price range or tips on the actual change out. Thanks, Jim.

Sounds to me like you lost 12 VDC control power which is supplied to the thermostat from the furnace. The furnace gets it from the Appliances fuse in your Power Center. Does your A/C work? It's pretty hard for those analog thermostats to suddenly "go bad".

[Trophy1200]

I had a similar problem with the thermostat. Tried it one day when running my gen and engine for their monthly exercise. All good.

Next time, around 3 weeks later, turned on thermostat for heat, nothing, no blower, nothing.

Carried out my diagnosis and found slider switch on thermostat would work for fans and A/C but nothing for furnace. I bypassed the thermostat and the furnace fired up first time and heated correctly.

I ordered the digital replacement from Amazon which is due to arrive tomorrow, so I guess I know what I’m doing at the weekend.

[04fxsts]

Originally Posted by 16ACE27

Sounds to me like you lost 12 VDC control power which is supplied to the thermostat from the furnace. The furnace gets it from the Appliances fuse in your Power Center. Does your A/C work? It's pretty hard for those analog thermostats to suddenly "go bad".

Yes, the tech from DE not only went through the troubleshooting sequence for the furnace board but also the thermostat. Years ago I had the board for the water heater in our old travel trailer and DE went through troubleshooting for that. He said I might try contact cleaner on the slides but that did not help. Jim.