The A/C compressor relay provides power to engage the A/C compressor clutch. The relay is usually located in the fuse box under the hood, or, less often, near the A/C receiver dryer or mounted on the firewall in the engine compartment. The relay usually has three electrical terminals: one for battery voltage, one for ground, and one for output to the compressor clutch. Sometimes the terminal for battery voltage also incorporates the power supply for other components, such as the radiator cooling fan relay.
