RV Repair: AC Thermostat, propane furnace, volt power

Question
We removed a propane furnace from our Arctic Fox that was connected to a dual furnace / AC thermostat.  Now the AC unit (Coleman Mach with matching thermostat) will not start up when we switch it to cool.  We checked the wiring diagram and it looks like the units are independent other than being on the same circuit board.  We checked across the fuse and the negative wire (red and blue in this case) and do not find any power.  On looking at the furnace wires all we see are a white and black (hot,negative) and a gray wire (igniter?).  Is it possible that we disconnected the power to the thermostat when we unhooked the furnace?  If not, what is likely cause of problem (we checked fuses and verified 12V is available at the panel)?

Answer
Mel, Coleman air conditioners do not make the 12 volt power. This comes from elsewhere. You should be able to open up the inside ceiling cover and in there you will see a box with either 4 or 5 wires on it depending on what kind you have, but one of those wires should be a 12 volt positive wire and if there is no power there then try checking back from there. You should be able to even see which one it is as they are usually marked. Then you will know the color wire that you need to find and check. It is hard for me to say hoe they ran the power to those particular units. Usually there are 4 wires to the furnace and 2 are to the T-Stat. If they got the power from the furnace then yes you may have disconnected it. You might not need to hook them all up but you might need to hook the hot to one of the T-Stat wires to get power back. Thanks, Bill