Our thermostat died yesterday, but after replacing the dead batteries with fresh batteries, and confirming the lcd screen was operable, our ac no longer turns on. As a result, the compressor does not kick in, and there is no. White-rodgers 975 5-1-1 Day Programmable 4-inch Universal Thermostat By White-rodgers 8738 The W Programmable Thermostat Digital Thermostat Home Thermostat Be sure to replace the batteries in the thermostat. Ac thermostat not turning on . If the thermostat does not turn on, it could also be a case of dead batteries. I have attempted a factory reset on the thermostat, and i do hear a quiet but definitive click when i believe it is attempting to activate the hvac unit, but that's as far as it gets. Either we’re talking cool air or hot air,. Set the thermostat to its lowest temperature, or if your thermostat has a heat off cool or fan auto off control, set the control to cool and fan to auto. Turn off the power at the wall before doing any investigat...