What directly controls the AC compressor 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’.

How do you test an AC relay?

The only tool required to check a relay is a multimeter. With the relay removed from the fuse box, the multimeter set to measure DC voltage and the switch in the cab activated, first check to see if there are 12 volts at the 85 position in the fuse box where the relay plugs in (or wherever the relay is located).

How do I know if my AC compressor relay is bad?

Common signs include inconsistent cooling, not hearing a click from the compressor turning on, and no cold air.

How do I test my AC compressor relay?

Unplug any relay terminal wiring with the interior car A/C controls in the “off” position. Check all three wires with the test light; with the engine running, the wires should all be inactive. With the engine running, turn the A/C control or switch to “on” at the dashboard. Check the three wires again.

How much does an AC relay cost?

Replacing an AC relay switch costs $100 to $300 with professional installation or $10 to $30 for the relay alone. The relay turns on the AC’s outdoor condenser unit.

Where is the AC relay located?

The relay can be mounted on the fire wall or on the fender well. A/C control installations typically have a three-wire connection for the relay. One wire is a ground, one wire is the input from the interior control panel, and one wire is the power feed to the A/C compressor clutch.

How do you check a relay to see if it’s bad?

Grab a multimeter and set it to Ohms. Touch the leads across the electromagnet coil pins and measure resistance. Anywhere from 50-120 ohms is OK. Out of range or open means a bad electromagnet coil winding and time for a new relay.