Thermostat Troubles with Furnace

[Hareball]

I replaced my old Atwood mechanical thermostat in our 2013 Somerset Sun Valley with a Honeywell PRO 1000 Vertical Heat Non-Programmable Thermostat. I read and saw YouTube videos that showed this was an easy replacement. When I installed the thermostat, it was 99 degrees in the trailer. I had to wait for things to get below 89 (in the evening) today so that the thermostat could be set to 90 (the max) for testing. Upon doing so, the thermostat immediately turned the fan on (expected). I would hear the igniter clicking and then the thermostat would appear to reset - heat never came. This would keep happening. Gas was open and worked the other night (it was much cooler) with the Atwood thermostat.

During the install, I did have to reduce the wires a bit in order to fit into the mounts on the new thermostat - could that be the cause? The wires from the furnace are much thicker than a house thermostat will take, but they align w/ the connections (W and R). I merely removed strands - probably not the best way. Should I have used wire nuts with thiner wire to step down from the thermostat to the feed that drives to the furnace? Or is this just not meant to work? Or was it perhaps too hot out? Logically, I would never actually use a heater to warm up the trailer to this level.

I really don't want to order a replacement Atwood thermostat - they're junk. The off switches on them constantly get stuck (why I went to replace ours) and their temperature setting is comically bad.

 

[fredhead]

I changed my thermostat as well with a Honeywell digital one. I solder spliced into the original wiring with smaller wires and have it so that I can hang it on the wall by the door, and store it in the cabinet by the door when the pup is closed up.

The thermostat is nothing but a switch activated by temperature level that you set. For testing, first I would replace the thermostat with a simple switch. That way you can turn the furnace on and off no matter what the temperature is and ensure the furnace is working correctly.

Then I would take the thermostat inside the house where the temp is lower and connect an ohmmeter to the connections for the furnace leads. When you increase the temp setting above the ambient temp, you should show a short, that is the thermostat "switch" should close. This will test both parts of the circuit independently. With the temp so high in the pup it is hard to make the furnace come on with the thermostat.

 

[KeizerTrailer]

Chances are you did nothing wrong during the install. As long as you hooked it up correctly, it will work as long as the temperature threshold is large enough to warrant the trigger of the thermostat.

 

[Hareball]

Chances are you did nothing wrong during the install. As long as you hooked it up correctly, it will work as long as the temperature threshold is large enough to warrant the trigger of the thermostat.

I would understand that, but I could hear the igniter trying to light the gas - it just never did. After the igniter clicks, the thermostat was clearing like it was resetting and then the process would repeat. I let it go for 5 or 6 attempts. It was 86 in the trailer and I had the thermostat set to 90.

 

[KeizerTrailer]

Have you checked your furnace is properly working?

 

[Raycfe]

As others have stated ........... connect the 2 thermostat wires together and the furnace should run. Then the temperature and new thermostat are out of the picture.

 

[Hareball]

Have you checked your furnace is properly working?

Yes, it worked fine the day before using the old thermostat, although the interior temperature was not the same.

 

[Hareball]

As others have stated ........... connect the 2 thermostat wires together and the furnace should run. Then the temperature and new thermostat are out of the picture.

Agreed - I need to rule out that there is nothing wrong w/ the new thermostat. I'll give that a try next time I have it setup.

 

[Raycfe]

Just to recap a couple of basic things.
Like the stove first to bleed off any air in the lines
And remember that the fan runs before and after the furnace runs

 

[csmorris]

I replaced mine with a digital when I was having furnace issues. Turned out I had to replace the circuit board.

 

[Kdague]

Your thermostat is designed for 24 volts. Furnace probably only runs off of 12 volts. If TStat dies out when it tries to light it’s probably because it’s dropping to too low of voltage for TStat to stay on. I would check voltages and confirm this. But I tried adding a digital one in my camper and could never get it to work. Probably need a TStat that doesn’t really on supply voltage to keep it on. Like a battery operated TStat.

 

[fredhead]

Your thermostat is designed for 24 volts. Furnace probably only runs off of 12 volts. If TStat dies out when it tries to light it’s probably because it’s dropping to too low of voltage for TStat to stay on. I would check voltages and confirm this. But I tried adding a digital one in my camper and could never get it to work. Probably need a TStat that doesn’t really on supply voltage to keep it on. Like a battery operated TStat.

The thermostat I have is this one

https://www.lowes.com/pd/Honeywell-Home-Digital-Non-Programmable-Thermostat-Electronic/5002570463?cm_mmc=shp-_-c-_-prd-_-plb-_-ggl-_-LIA_PLB_171_Air-Circulation-_-5002570463-_-local-_-0-_-0&ds_rl=1286981&gclid=Cj0KCQjwjbyYBhCdARIsAArC6LISBQeFpGusBmb2sJsOcokMmq6enbRtgmdZMlI9bBqNPZjfsgQG7JgaAsMXEALw_wcB&gclsrc=aw.ds

It runs on two AA or AAA batteries and is an on-off switch that you set to a temperature.

 

[Hareball]

Your thermostat is designed for 24 volts. Furnace probably only runs off of 12 volts. If TStat dies out when it tries to light it’s probably because it’s dropping to too low of voltage for TStat to stay on. I would check voltages and confirm this. But I tried adding a digital one in my camper and could never get it to work. Probably need a TStat that doesn’t really on supply voltage to keep it on. Like a battery operated TStat.

The thermostat in my case is battery-operated. It just has a heat on/off switch and two buttons (up/down) to set temperature. https://www.honeywellhome.com/us/en...t-non-programmable-thermostat-th1100dv1000-u/

 

[Ada McKin]

sounds like you need a mechanical thermostat like the ones used for electric baseboard heaters that can carry amps, unlike the milliamp thermostat you are trying to use, others said it right short the 2 wires and see if it runs normal, if so get a mechanical thermostat.

 

[TSQ]

Try replacing the thermostat batteries.

Sounds like the thermostat batteries are nearly dead - when the thermostat closes its internal relay to signal the furnace to turn on the additional power draw causes it to reset.

I have a Honeywell digital thermostat and it works really well.

edit: Which furnace?

 

[Kdague]

Yeah sorry about that. When I looked it up, I used Amazon and it said it was a 24 volt TStat. Definitely try new batteries and test stat when it’s not connected. Make sure u hear it click when there is a call and that it doesn’t seem to dim out too much. Also test and make sure your furnace works by holding wires together. Make sure your wires aren’t touching the C or each other on the connections of the TStat. Process of elimination will bring u to the point of where it’s having the issue.