How to Troubleshoot a Nonworking Thermostat

Check the circuit breaker that powers your heating system to be sure that it is on. Also check to be sure the power switch located near your system is on. The thermostat is powered by the heating system. Change the batteries in a digital thermostat. If you have recently lost power, you may need to reprogram your digital thermostat.

Remove the cover of the thermostat and use a small paintbrush to gently brush the connectors to clear any dust or spider webs that may be blocking the connection. Do not touch any of the interior parts with your fingers.

Inspect the wires inside the thermostat. Tighten any loose connections or repair any broken wires. If any corrosion is present, remove the wire and clean the terminal.

Create a jump between connections to test the thermostat. A thermostat's terminals are marked with "Y," which is usually a blue wire; "W," a white wire; "G" is typically black; and "R" is red. Use a short piece of wire with the ends stripped away to create a jump between connections. Place one end of the jump wire on the "Y" and the other end on the "G." If the fan comes on during this connection, your thermostat could be faulty.The electricity will need to be on for this test.