HVAC Repair Service: A homeowner reported that their thermostat display had suddenly gone blank, causing the HVAC system to stop responding. After inspecting the unit, I found a blown low-voltage fuse in the air handler that was preventing power from reaching the thermostat. I replaced the fuse, checked the control wiring for additional faults, and confirmed proper voltage to the thermostat. Once restored, the thermostat powered on normally and the HVAC system resumed full operation.