Replacing an Air Conditioning Contactor
January 1, 2017

If you are a do-it-yourself-er, one of the easiest repairs you can make yourself is replacing the contactor on an air conditioning (AC) unit.

A contactor is an electrical component switch and is used to control the AC’s thermostat and gives energy to the fan and compressor of the AC’s outer condensing unit.

The signal sent to a magnetic coil is energized by the metal contacts and is delivered when the AC unit is turned on and the thermostat temperature is set. With continued use, the contactor surfaces are covered in layers of carbon from frequent circuit use, and when this happens, the contactor ceases to work effectively and your AC unit with emit a humming or chatter noise.

That’s when it’s time to replace the contactor, and here’s how the repair process the experts at Certified Air Conditioning┬árecommend:

What You’ll Need:

  1. A voltmeter to read output
  2. A pair of pliers- A screwdriver
  3. A pair of needle-nose pliers
  4. Additional Sta-Kon disconects
  5. A pair of wire strippers

Where is the Contactor Located?

It’s typically located where the electrical connection to the unit is joined, and is a compact, dark-colored (either brown or black) block with electrical disconnects on both the left and right sides.


  1. Make sure the power is off have the correct replacement contactor nearby.
  2. Take off the mounting screw.
  3. Secure the new contactor in place and attach the voltage wires to the sides of the replacement contactor.
  4. At the bottom of the contactor, reconnect the wires from the disconnect.
  5. Turn the power on, position the thermostat to “cool” and see if the contactor connects. When you see that it does, turn the power off again
  6. Check the terminals with your voltmeter to make sure there is no power and connect the wires at the top of the contactor to the fan and compressor.
  7. Put the cover on and turn disconnect back on.
  8. Check the unit frequently to ensure the cool temperature is kept.

Tips when buying a replacement contactor:

  • Make sure the control voltage rating is accurate.
  • Make sure the amperage is accurate.
  • Purchase a contactor with the same amount of poles as the previous contactor.
  • Purchase a contactor with terminals that match the previous contactor.

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