Replacement Thermostat Troubleshooting Help

[theguyoverthere]

I followed the forums and many of them said to upgrade to the RV Comfort Coleman Mach Thermostat. I'm in a bit of a bind now because we are camping Friday and will need some heat and I can't get the thermostat to work properly. My issue is that the furnace fan runs constantly. It will occasionally turn off for 1 second and turn on again. While the thermostat is on Auto. The heat doesn't' run constantly, just the fan.

I only have 2 wires going to the thermostat. Tracing it back to the Furnace, the White wire connects to the wire labeled Thermostat on furnace and the White/Red wire connects to the wire labeled +Thermostat. What am I doing wrong? Did I waste money and buy the wrong thermostat? Any troubleshooting I an try?

Thanks.

[curver900]

have you tried turning it to heat off of auto? if it still does the same thing then likely your furnace isn't firing.. LP open? something keeping it from igniting?

[DanNJanice]

You need to give us a little more information about your setup.
First, what model number is your new thermostat?

Do you have any display on the thermostat when it is connected?

Does it have batteries and are they installed?

You need one that runs entirely by battery power. I used a LuxPro 511LC 5-2 thermostat when I replaced mine.

In a two wire system like you have, the thermostat just connects the wires together, when it calls for heat. Try disconnecting the two wires going to the furnace and twisting them together. The furnace blower should turn on, and after a few minutes you should feel heat. When you untwist the wires, the furnace should turn off in a couple of minutes. Note, there may be +12V on one of the wires, so avoid touching any metal objects with the wires. Turn off/disconnect the batteries if you are not comfortable with this step.

[theguyoverthere]

See my answers in blue.

Originally Posted by DanNJanice

You need to give us a little more information about your setup.
First, what model number is your new thermostat?
Coleman 83303862 Digital Thermostat

Do you have any display on the thermostat when it is connected?
Yes, it displays the current temp and set temp

Does it have batteries and are they installed?
No it doesn't use batteries

You need one that runs entirely by battery power. I used a LuxPro 511LC 5-2 thermostat when I replaced mine.

In a two wire system like you have, the thermostat just connects the wires together, when it calls for heat. Try disconnecting the two wires going to the furnace and twisting them together. The furnace blower should turn on, and after a few minutes you should feel heat. When you untwist the wires, the furnace should turn off in a couple of minutes. Note, there may be +12V on one of the wires, so avoid touching any metal objects with the wires. Turn off/disconnect the batteries if you are not comfortable with this step.

[theguyoverthere]

Originally Posted by curver900

have you tried turning it to heat off of auto? if it still does the same thing then likely your furnace isn't firing.. LP open? something keeping it from igniting?

The fan runs on auto or on on constantly even with the switch being in the off position or heat position. When I turn it on heat and the temp gets low enough, the heat does come on and comes through the trailer. I'm worried about draining the trailer batteries with the fan constantly running no matter what.

[Sundancer330]

Do you have the model number of the old tstat, coleman has a chart that shows if the new one is compatible.

https://www.makariosrv.com/content/M...nt%20Guide.pdf

[DanNJanice]

Originally Posted by theguyoverthere

The fan runs on auto or on on constantly even with the switch being in the off position or heat position. When I turn it on heat and the temp gets low enough, the heat does come on and comes through the trailer. I'm worried about draining the trailer batteries with the fan constantly running no matter what.

Hmmm, something does not sound quite right. With only two wires to the thermostat you cannot have separate control of the fan and the burner.
Also, if you do not have any batteries in the thermostat, you would need at least three wires, Positive, Negative, Call for heat.

[theguyoverthere]

Originally Posted by DanNJanice

Hmmm, something does not sound quite right. With only two wires to the thermostat you cannot have separate control of the fan and the burner.
Also, if you do not have any batteries in the thermostat, you would need at least three wires, Positive, Negative, Call for heat.

I'm hoping this is the same thermostat you mentioned. I just ordered it from Amazon.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[norty1]

I would put the old thermostat back in and enjoy your camping trip. Deal with it when you get back!

What type ac do you have?

[theguyoverthere]

Originally Posted by norty1

I would put the old thermostat back in and enjoy your camping trip. Deal with it when you get back!

What type ac do you have?

I wish. I accidentally obliterated the old one back in April when I removed it trying to get the mounting screw that was jammed into it and hadn't gotten around to working on this project again until now. So I don't have the original thermostat anymore. I don't recall the type of A/C I have. I'll have to look when I get home from work.

[DanNJanice]

Originally Posted by theguyoverthere

I'm hoping this is the same thermostat you mentioned. I just ordered it from Amazon.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Yes, that is the one. It will need a battery, so make sure you put one in.
Just connect your white/red wire to the RH and RC terminal. Then your white wire to the W terminal.
One nice feature of that thermostat, other than the price, is that you can control the amount of hysteresis.

Here is a link to my wiring diagram.

[denn888]

Originally Posted by theguyoverthere

I followed the forums and many of them said to upgrade to the RV Comfort Coleman Mach Thermostat. I'm in a bit of a bind now because we are camping Friday and will need some heat and I can't get the thermostat to work properly. My issue is that the furnace fan runs constantly. It will occasionally turn off for 1 second and turn on again. While the thermostat is on Auto. The heat doesn't' run constantly, just the fan.

I only have 2 wires going to the thermostat. Tracing it back to the Furnace, the White wire connects to the wire labeled Thermostat on furnace and the White/Red wire connects to the wire labeled +Thermostat. What am I doing wrong? Did I waste money and buy the wrong thermostat? Any troubleshooting I an try?

Thanks.

Dont know if this helps, I had 6 wires coming out of the wall, 4 wires are grouped in the black casing, I just connected wire for wire, the loose yellow and red were connected together but came loose when I pulled the wires out of the wall, I have one AC and the heater on the thermostat.