Mechanic Glossary

A/C Compressor Relay

An electromagnetic switch that routes high-current power to the A/C compressor clutch coil when commanded by the climate control computer.

The A/C compressor relay is the switch that engages the air conditioning compressor. When you press the A/C button on the dash, the engine computer sends a low-current signal to the relay. This activates a coil inside, closing the contacts to send 12-volt battery power directly to the compressor clutch electromagnet. Without this relay, the high amperage drawn by the clutch coil would burn out the dashboard switches.

Relays fail due to worn contacts or burnt internal windings. If the relay sticks open, the compressor will never turn on. If it sticks closed, the compressor clutch will stay engaged constantly, draining the battery even when the vehicle is turned off.

Frequently Asked Questions

The air conditioning system will stop blowing cold air because the compressor clutch is not receiving power to engage.

You can swap it with an identical relay (like the horn relay) in the fuse box to see if the A/C starts working. You can also use a multimeter to check for resistance and continuity.

It is located in the underhood fuse block. Check the diagram on the fuse box cover for the label A/C CLUTCH or A/C COMP.

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