Furnace Thermostat

[Luckydog671]

Hi all,

On our last trip we had some issues with the factory-installed furnace sporadically not working. At one point I thought it may be a gas issue - thought I had it figured out by lighting the stove burner before attempting to light the furnace. Only worked the one time, then it would not work the next time.

I concluded it was probably either the factory thermostat had gone bad or the gas valve was going bad. The cheapest option was replacing the thermostat so thought I'd try that first. Lo and behold, I came across a used Honeywell digital thermostat at a thrift store for only $2. I figured even if it doesn't work any longer, it wasn't gonna break the bank! So I just put some batteries in it and I think it still has some life left but I'm wondering how to hook it up? There are only two wires on the old thermostat. Any HVAC experts out there? I've attached photos of old and new.

Thanks,

 

[Hersbird]

I'm a mailman but it should be red to the R and white to the W/aux
It should say in the book there if anything else should be jumpered. It is just controlling the heater not the A/C right?

 

[Luckydog671]

I'm a mailman but it should be red to the R and white to the W/aux
It should say in the book there if anything else should be jumpered. It is just controlling the heater not the A/C right?

Thanks Hersbird, first time I've ever changed a thermostat so didn't realize it was that simple. Yes, it will only be used for heat.

 

[Richard-HILO]

Luckydog, FYI most electronic thermostats are looking for a 24 volt AC power source, and you will be supplying 12 volt DC. If you want to verify that your original thermostat is at fault, just short the two wires that were connected to the thermostat and the heater should come on, if it does then the thermostat is probably at fault. You might want to do this test several times to eliminate a fluke test. A quick note, you might try to clean the contacts on the (off/on) switch of your original stat. Good luck

 

[Hersbird]

Did this work? As long as the digital thermostat has batteries it should work on 24v AC or 12v DC. I plan on doing mine this week but will just buy a simple non programmable one at Walmart.
My original works but has a huge temp swing from chilly to sweating.

 

[Luckydog671]

Luckydog, FYI most electronic thermostats are looking for a 24 volt AC power source, and you will be supplying 12 volt DC. If you want to verify that your original thermostat is at fault, just short the two wires that were connected to the thermostat and the heater should come on, if it does then the thermostat is probably at fault. You might want to do this test several times to eliminate a fluke test. A quick note, you might try to clean the contacts on the (off/on) switch of your original stat. Good luck

Thanks, Richard. I tried the test you mentioned (several times) and the blower started everytime but the actual heater never fired up. Could that be due to the fact that is was 92 degrees inside the trailer? Think I'll try it the morning when it's cool . . .

 

[Luckydog671]

Did this work? As long as the digital thermostat has batteries it should work on 24v AC or 12v DC. I plan on doing mine this week but will just buy a simple non programmable one at Walmart.
My original works but has a huge temp swing from chilly to sweating.

I'm going to try it tomorrow morning. Not sure if this programmable thermostat will work or not so may end up getting a non-progammable if need be. I just received the new Trailer Life so will read the article that was mentioned in a different thread.

 

[RichR]

I'm going to try it tomorrow morning. Not sure if this programmable thermostat will work or not so may end up getting a non-progammable if need be. I just received the new Trailer Life so will read the article that was mentioned in a different thread.

The programmable one will probably work but you really don't want to program it unless you stick to a firm schedule. The non-programmable is a much better choice and simpler to use, and may use less battery power.

Touching the wires together should make it come on to heat, not just start the fan. You may have other problems there. Consult the furnace manual troubleshooting section to see if there are any suggestions.

 

[Fountain-FRF]

The temp in the trailer should have no effect on the furnace if you are touching the two wires together. You are bypassing the very item that detects rise and fall of temperature. You may be looking at furnace problems, not thermostat.

 

[Hersbird]

We bought a $23 Honeywell digital non-programmible tstat from Walmart last night and it works great. Red to one of the "R" posts, they are jumpered, and white to the "W". It shows inside temp all the time and just move it to the heat setting and then push the up or down arrows to set desired temp.

 

[RichR]

We bought a $23 Honeywell digital non-programmible tstat from Walmart last night and it works great. Red to one of the "R" posts, they are jumpered, and white to the "W". It shows inside temp all the time and just move it to the heat setting and then push the up or down arrows to set desired temp.

That may be the same one I got. You will enjoy a more even temperature with out the big swings.

 

[Luckydog671]

Looks like I have a furnace, not a thermostat, problem. The manual is pretty useless regarding troubleshooting. Any suggestions on what to look for?

Thanks,

 

[RichR]

You could have low gas pressure, there may be an air restriction somewhere, or a couple other possibilities. Enter the Make and model in Google and you should get a number of sites, including YouTube, with service manuals, etc.

 

[jhoward22]

sorry to bring back an old thread , but has anyone hooked up the air conditioner and heater to a digital thermostat , all in one kinda thing ? im thinking about adding a digital thermostat in my 22 ft hi lo and it would be pretty cool ( no pun intended ) to get the air conditioner on the same thermostat . my air conditioner controls are located on the side of the camper now instead of the middle so i have access to the wiring and could get wires to the thermostat pretty easily . im no hvac guy , but im hands on if someone knows the correct wires needed from the ac to the thermo , id like to get it wired in . any info would be awesome , thanks

 

[RichR]

sorry to bring back an old thread , but has anyone hooked up the air conditioner and heater to a digital thermostat , all in one kinda thing ? im thinking about adding a digital thermostat in my 22 ft hi lo and it would be pretty cool ( no pun intended ) to get the air conditioner on the same thermostat . my air conditioner controls are located on the side of the camper now instead of the middle so i have access to the wiring and could get wires to the thermostat pretty easily . im no hvac guy , but im hands on if someone knows the correct wires needed from the ac to the thermo , id like to get it wired in . any info would be awesome , thanks

I don't think you can do that easily. If I'm correct, your A/C has manual controls with knobs. You would need a relay of some sort that would allow you to put power to the A/C because the thermostat is not made to handle the power load.

 

[Hersbird]

when you touch the wires together it takes a few seconds on mine but then you hear the fan start on the heater's blower and then the gas valve click open and the igniter click. Then it lights the gas which makes a woosh and it's working. What part doesn't happen? If it's totally dead I would look at fuses. If the gas valve doesn't open then there is a switch that senses the fan is running and another that senses if the flame is too big, either can keep the gas valve shut. If the gas valve opens but it doesn't ignite then the igniter might be bad or there may be no gas getting to the furnace. My furnace at home was really acting weird, gas valve sometimes not opening and sometimes working fine and it turned out to be a bad ground of all things.