Thor Forums

[javelin]

Well Jevad, I viewed your excellent videos. Well done. Now if only the forum can help translate them into a solution for you. Although I don’t have a Coleman Mac thermostat schematic I think it is fair to say that when the +12vdc feed (red wire) on the thermostat is only reading 2 VDC, the call for heat relay in the thermostat is not going to operate (click on) properly or at all to connect red to white wire and actually call for heat at the furnace end.
So to me the issue is why the 12vdc is dropping to 2ish vdc? Maybe the power/reset switch in the furnace is flaky with damaged/dirty or just poor contacts inside? Strange because it hardly gets used. When you have “your problem” occurring measure feeder (coach fuse) side voltage on the furnace switch. Should be 2 vdc (based on schematic) if trouble is on. Then turn off the switch and see what you measure. Jumps up to 12vdc then the issue is on the furnace side of the switch......or the switch itself. In effect you need to isolate where the flaky part/wire/splice/crimp/connector is occurring. Since bumping the area seems to fix the intermittant problem this could take a while to track down. I would also operate the switch several times if it looks to be the culprit. You could also temporarily jumper the switch and see if the trouble stops occurring. Don’t you just love those intermittant problems? Don’t give up now you are home and winterized.