The A/C relay is an electromagnetic switch. It uses a low-current control signal from the dashboard switch to close high-current contacts. This sends 12-volt battery power directly to the compressor clutch. This design keeps high currents out of the cabin, preventing wires from melting.
Mechanic Glossary
A/C Relay
The electrical relay that switches power to the A/C compressor clutch.
Frequently Asked Questions
In the engine compartment fuse box. Check the layout diagram on the cover.
The blower fan works but the compressor clutch does not click on, or the compressor runs constantly, freezing the system.
Yes, if the relay contact points stick closed, the compressor clutch will stay engaged and draw power even when the car is turned off.