How To Replace a Contactor Relay on an Air Conditioner or Heat Pump

By | April 26, 2022

How To Replace a Relay Contactor on an Air Conditioner or Heat Pump
The contactor relay in an air conditioner or heat pump is what controls the voltage coming into the unit.

The main power, usually 220 volts, comes from a breaker and is fed into the contactor.
What is a Contactor on an Air Conditioner or Heat Pump
The contactor is controlled by the thermostat to turn on/off the unit, by letting 220-volts into the HVAC system.

The thermostat controls the contactor with 24-volts that is sent to a coil in the contactor, creating a magnetic field that pulls it closed and sends power to the unit.

The 24-volts is controlled by the thermostat setting, which turns the unit on or off depending on the temperature.

Contactors come in three styles single pole, double pole, and triple pole.

Example Single Pole Contactor on Amazon
Packard C140A 1 Pole Contactor Coil Contactor, 40 Amp, 24V

On one side, power will be attached from the breaker or disconnect and labeled L1 and L2.
HVAC contactor relay
On the other side, power to the HVAC system will be attached labeled T1 and T2.

On the sides are blue and yellow wires, which is where the 24-volts comes in from the thermostat.
How To Replace a Contactor on an Air Conditioner Heat Pump Update
When the thermostat reaches the set temperature, 24-volts is sent to the contactor, which will magnetize the coil and activate it.

The small plastic cover can be taken off to examine the contacts. The center can be pressed on to see how they are touching when pulled in by the coil.
inside a hvac contactor relay

How To Replace a Contactor on an Air Conditioner or Heat Pump

  1. Power down the unit at the disconnect or breaker.
  2. How To Install a Hard Start Kit Step 1.1

  3. Examine the wiring take pictures or write them down, note the L1, L2, T1, and T2 wires.
  4. How To Replace a Contactor on an Air Conditioner Heat Pump Step 1

  5. Remove the bolts holding the old contactor in place.
  6. How To Replace a Contactor on an Air Conditioner Heat Pump Step 2

  7. Screw the new contactor into place.
  8. How To Replace a Contactor on an Air Conditioner Heat Pump Step 3

  9. One wire at a time, remove the wires from the old contactor to the new one.
  10. How To Replace a Contactor on an Air Conditioner Heat Pump Step 4

  11. Power back on and test the unit.
  12. How To Replace a Contactor on an Air Conditioner Heat Pump Step 5

Summary
The above is a simple breakdown of a contactor relay and how to replace a bad one.

The information will apply to Single Pole, Double Pole, and Triple Pole contactors.

Some units will have the 24-volts placed only on one side or at the front. While not common, some units may have a slightly different layout.

Replacing a heat pump or air conditioning relay is a straight forward simple job as long as safety is taken into account, such as turning off the power.

Replacing the wires back correctly will be the only real concern; as long as pictures or notes are taken prior to removing the relay, this should be a quick and easy job.

Have you replaced a contactor on an air conditioner or heat pump? Let us know your thoughts below.

 




 

One thought on “How To Replace a Contactor Relay on an Air Conditioner or Heat Pump

  1. David Reeser

    As a homeowner where can I buy a contactor for a goodman heatpump for a model number GSZ130481. SER NUMBER 120515392 HEATPUMP. In or around Richmond va

    Reply

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