Close

Air Conditioner (A/C) Relay

The air conditioner (A/C) relay, is a relay used to send electrical power to the air conditioning compressor, and air conditioning compressor clutch when the system is turned on. It operates just like any other relay, and is often controlled by a button labeled ‘A/C’.

Symptoms of Wear or Failure of the A/C Relay

  • Air conditioning compressor works intermittently (randomly): as the relay wears out, many times they will turn on the A/C compressor at random intervals. This is because the electrical contacts inside the relay may not be totally worn, but they do not have a good connection.

  • Vents blow only warm air: while this could be a few other issues, and most commonly is, the A/C relay may have failed, preventing the A/C compressor from receiving the signal to start. This will be accompanied by the absence of the normal ‘click’ sound heard when turning on the A/C.

  • A blinking A/C light will alert you to an air conditioning issue, but not normally if the relay has failed.

Related Repair Advice

  • While simply replacing the relay seems cheap, fast, and easy, the result is normally just as cheap. If you suspect the relay has failed, it should be tested prior to replacement.

  • If the relay clicks when the A/C is turned on, this does not mean that power is flowing through the relay, it only means the relay is receiving electrical power. This is another reason testing is important, as the relay could seem good, but not route power to the A/C compressor.

  • There are other switches that control the A/C system, and a few of them will prevent the A/C from running by interrupting the signal to the A/C compressor. This is yet another reason why diagnosing the issue properly before buying parts is essential.

  • Many vehicles that use A/C compressor control valves always have the compressor running, and some will not use an A/C relay. Instead, the amount of work the compressor can do is limited by the compressor control valve, and moderated by the engine control module.

0 User Comments

Sign in to comment
Why RepairPal?

Asset 71
High Quality Repairs
Your auto repair done right, only the work you need with no add ons.
Asset 72
Never Overpay
Our free estimator calculates a custom price for your vehicle repair.
Asset 73
Guaranteed Repairs
Rest easy knowing you're covered by our RepairPal Nationwide Warranty.