My AC unit has the thermostat indoors, a unit in the crawl space and the outdoor unit. Everything was working until I had a contractor come out and add insulation in my crawl space. Now the heat/air will not cut on. I have checked:
1) Fuses in fuse box
2) Outdoor breaker box
3) Thermostat has batteries (working)
4) Unit is set to cool
What else could it be that is preventing anything from cutting on when I turn on my AC from the thermostat? (heat doesn't work either, so it's not limited to AC)
Best Answer
The thermostat cable could have been pulled loose or broken at some point. When the thermostat is turned on, it should supply voltage to a relay on the AC unit and that normally makes an audible "click". Checking the voltage on the thermostat wires leading to that relay should show 24vac (alternating current).
If there is no voltage, you can check the wire for breaks along it's path. Because it is low-voltage, it doesn't have the same rules on splices and how its run as the main electrical wiring so it can get damaged more easily. An existing splice could have been pulled loose.