Symptoms of a Faulty or Faulty AC Compressor Relay

Common symptoms include intermittent cooling, no click when compressor turns on, and no cold air.

Almost every vehicle electrical system is powered by some sort of switch or electrical relay, and the AC system and compressor are no exception. The A/C compressor relay is responsible for supplying power to the A/C compressor and clutch. Without this relay, the A/C compressor will not have power and the AC system will not work.

The air conditioning compressor relay is no different from other electrical relays - its electrical contacts wear out or burn out over time, and the relay must be replaced. When the A/C compressor relay has failed or is starting to fail, it will begin to display symptoms indicating that it is time to replace it.

1. Uneven cooling

The air conditioning compressor is powered by a relay. If it is not working properly, then the air conditioning system will not be able to properly produce cold air. When the relay begins to fail, it can supply the compressor with weak or intermittent power, resulting in weak or intermittent operation of the air conditioner. AC may work fine in one instance and then shut down or become unstable in another. This could be a potential sign that the relay may be failing.

2. The air conditioner compressor does not turn on

One of the most obvious signs of a bad AC relay is that the compressor won't turn on at all. In most cases, when the air conditioner is on, you can hear the compressor turn on. It usually makes a familiar clicking sound when the clutch is engaged. If, when turned on, you can’t hear how the clutch turns on, then it may not be energized due to a failed relay.

3. No cold air

Another sign that the AC relay may be failing is that there will be no cold air coming from the AC at all. If the relay fails, the compressor will not work and the air conditioning system will not be able to produce cold air at all. While there are several reasons why an air conditioner might stop producing cold air, a bad relay can be one of the most common.

If you are having problems with your AC system and suspect that your AC relay has either failed or is starting to fail, we recommend having a professional technician diagnose it. If your AC relay turns out to be faulty, they can replace the AC relay if necessary.