Why isn't my HVAC unit responding to the thermostat?

When your heating, ventilation, and air conditioning equipment fails to respond to commands from your wall thermostat, it points to electrical power losses, loose wiring, or control board failures. First, check your thermostat display screen; if it is completely blank, a tripped circuit breaker or a blown low-voltage fuse on the indoor furnace control board has cut off power. Second, remove the thermostat faceplate and inspect the low-voltage wire terminals to ensure colored wires like R, W, Y, and G are securely fastened. Third, check for loose wire connections behind the unit. You can troubleshoot by replacing a blown furnace fuse and tightening terminal screws. You can verify that the communication problem is resolved when manual temperature adjustments successfully trigger your HVAC system to turn on.