Shut off the power to the heat pump. The 220 VAC breaker should be located on the building wall next to the heat pump. Remove the screws that secure the access panel to the electronic controls, then remove the access panel.
Cut the two sensor wires that attach to the defrost circuit board, if they are soldered onto the board, with the dykes. Strip the ends of the wires and install connectors with the crimpers on the wire ends as needed to connect to the board and transfer the wires to the new part. Remove the other wires one by one from the old board with the needle-nose pliers and, if needed, a small screwdriver. Reinstall them onto the new board one by one.
Unscrew the screws that mount the old board in place and remove it. Place the new board over the mount holes and reinstall the screws. Replace the cover of the electrical controls on the heat pump and then turn on the power at the circuit breaker.
Things You Will Need
- Wire stripper or razor knife
- Wire plug connectors (optional)
- Crimper tool
- Needle-nose pliers
- Small screwdriver (optional)
- Read the heat pump technical manual before you start the job to determine where the defrost board is located.
- Sometimes, more than two wires will need to be cut to change the terminal ends.
- Board mounts may also need to be replaced in some cases. A drill and bit may be required to make the mounting holes larger.
- Replace the coil and air temperature sensors if you are unsure they are working properly.
- When you replace the connectors on the board, make sure that they are not loose. If they are, then crimp them to make them attach securely.