Perhaps you often find yourself staring at your faulty thermostat in the house at times when you needed it most. Faulty wirings or slack connections can make your heating or cooling system malfunction. In order to fix your thermostat, you will need an artist's brush, a neon tester, batteries, a substitute thermostat, tape and pen, level or plumb line, screwdriver, and wire cutters or strippers.
- Be sure to turn off the power first. As with repairing all major electrical appliances, safety must com first. Cut the power to your heating and or cooling systems at the main circuit breaker or switch to be completely sure no electrical current will flow into it.
- Take out the thermostat. Some thermostat models have a cover plate. If that’s the case, remove the cover plate and then detach the body of the thermostat from a wired base plate held onto the wall. There are also models which are secured into the base plate without any bolts.
- Brush away all dust or grime from the thermostat. Clean the base plate as well. This is where the artist's brush will come in handy.
- Inspect for broken, worn out, and rusty wires and loose connections. Tighten any loose connections you find. For a worn out part of the wire, use wire cutters or strippers to cut it and shred about 1/2 inch of its insulation. Reconnect the wires afterwards.
- Go back to the main circuit and turn the power on to test the thermostat. This time, you have to check it with the thermostat's manual. Testing may involve disconnecting the power wire which is most of the time colored red and then tapping it to the terminal which is often marked as W with a white wire from the heater's transformer.
- Bypass the thermostat to ensure its cooling functions. In the same way as testing for heat, tap the disconnected power which is the red wire to the terminal for the cooling system.
If one or both of the just said procedures did not succeed, turn off the power and then inspect the thermostat wires on your heating system. Like for instance, detach the wires from the thermostat and transformer, attach them together at one end, and check for stability at the other end by using a continuity tester to one wire and penetrating the other wire. Replace the wires if the tester fails to light.
The following procedures apply to replacing the thermostat unit.
- Detach all wires from the base plate one at a time. Mark each wire with a tape that classifies its terminal connections. That could be the R, the Y, the W and so forth.
- Patch mounting holes or mount the cover ring that the new thermostat unit has. This step is for cases when the new thermostat base does not match with the old mounting holes.
- Raise the new thermostat to the wall. Make sure you position it according to the manufacturer's instructions. Normally, you can line up notches with a level or any perpendicular line you can find on the wall, or put a tiny level on leveling posts at the bottom or its circumference.
- Use the wiring diagram provided in the installation instructions. It's important to hook up the labeled wires to its appropriate terminals. Don’t forget to remove the tape while you make the connections.
- Put in batteries and set the thermostat. Afterwards you can attach the thermostat to the base and put the power back on.
Low voltage wiring, like thermostats, may not greatly hurt you but a small jolt can still surprise you or cause damage to the unit itself.