No D.C. Power at thermostat.

One of the fuses on the panel

It might also come from a circuit board in either the furnace or air conditioner.

Mandalay Parr wrote:
It might also come from a circuit board in either the furnace or air conditioner.

Thank you!!

Found where the red/white wire ran from the furnace loose. +12v achieved before it got too hot again today. Yesterday was miserable before I finally just ran a wire from the CBP to the compressor/fan.

Coleman usually get it from the furnace, DuoTherm/Dometic from the roof unit.

Ok so update on this. Air conditioner works perfectly.

The thermostat is a Honeywell residential digital battery powered unit. All of the wires have appropriate voltage, but when I change the thermostat to heat the thermostat itself gets warm/hot very quickly. Im thinking this means the white wire to the furnace has some sort of issue I haven't found yet. Anyone have any experience or tips on this?

try this thread Honeywell Thermostat mod mine just runs off its own batteries going on 2 years now still working. lots of you tube videos also you tube

What air do you have, what is hooked to RH and W on the thermostat ?

Coleman AC. There is a jumper between RH and R installed. This is hooked to the red wire from the furnace. W is hooked up to the white wire to the furnace.

Furnace works properly with red and white touching outside the thermostat.

The thermostat circuit board gets hot as soon as I set it to heating mode. Is it possible I got a bad Thermostat or more likely i'm missing something?

I mean I am literally disconnecting the white wire, touching it to the red terminal and the furnace starts right up, but with the white wire in its designated contact, the whole thermostat board heats up when I select heat.

back up a bit. Are you trying to wire in a new digital thermostat or is this an existing install? Normally, thermostats are used to switch "control lines". It looks like you are are trying switch wiring that is running your furnace (ie. high current / power).

budwich wrote:
back up a bit. Are you trying to wire in a new digital thermostat or is this an existing install? Normally, thermostats are used to switch "control lines". It looks like you are are trying switch wiring that is running your furnace (ie. high current / power).

My analog Coleman T-stat quit working so I am trying to get the Honeywell T-stat working properly. Air cond. compressor, fan, and thermostat are all operating properly while in cooling mode.

Whenever I switch the T-stat to heat, the T-Stat itself gets warm and the furnace never comes on.

I checked to see if the furnace was working by manually jumping the wires. The furnace operates normally with the wires jumped.