Furnace doesn’t work

dougrainer wrote:

stew47 wrote:
Ac doesn’t run

Then your problem is probably in the Wall tstat upper AC control board area. THIS controls both the AC and the furnace. Doug

Doug knows what he's talking about. The problem is the upper AC control board.

No 12 volt from coach to ac. Fuse is good from power distribution box/ fuse panel.

stew47 wrote:
Ac doesn’t run

Then your problem is probably in the Wall tstat upper AC control board area. THIS controls both the AC and the furnace. Doug

Ac doesn’t run

Does the roof AC run? Doug

What type of Thermostat. Many T-Stats today are digital electronic and have an internal battery. if dead no joy

My RV from factory used one of the A/C's to control the furnace (Front one) when I replaced the A/C I had to put in an new furenace stat

I got a 20 dollar mechnical mercury free (This is improtant) from Ace Hardware and a toggle switch and an LED indicator

Of the two, normally blue, wires one has 12 volt on it. this goes to the toggle (Which is mnounted beside the T-Stat I choose a rocker type) the other lead of the switch goes to the POSITIVE lead on the Led an the T-Stat
The other T-Stat lead to the other blue wire
The negative LED to Ground (it is a 12 volt LED indicator assembly)

Switch off = Furnace off
Switch on = LED on T-stat controls furnace
LED blinking (Slowly)( or dim = problem with wiring back at furnace

I jumped the wires at the furnace. I have dometic ac and I have dometic slide type thermostat.

DFord wrote:
Where did you jump the wires? At the furnace or at the thermostat. The only thing the thermostat is capable of doing is closing the circuit you say you're jumping. If you jump the wires at the furnace and it works but when you jump them at the thermostat it doesn't, you've got a bad wire between those two points.

Sometimes the air conditioner control box/board is also involved as a middleman between the thermostat and the furnace. If it's not getting 12V power or something it might not communicate betwixt the two. (On mine, there's definitely a relay on the air conditioner control board that is controlled by the thermostat and in turn controls the furnace. It's a Dometic air conditioner, originally with one of their slide rule style thermostats but since upgraded to a generic battery-powered digital one.)

Where did you jump the wires? At the furnace or at the thermostat. The only thing the thermostat is capable of doing is closing the circuit you say you're jumping. If you jump the wires at the furnace and it works but when you jump them at the thermostat it doesn't, you've got a bad wire between those two points.

Digital thermostat? Check for a blown fuse in the 12V load center. Make sure the thermostat doesn’t operate off it’s own battery.