P0645

Symptoms

• Check Engine light comes on
• The air conditioner does not turn on or operates intermittently
• Air conditioner button does not respond
• Warm air comes out of the air ducts when the air conditioner is turned on
• Extraneous noise when trying to turn on the air conditioner

Causes

• A/C compressor clutch relay malfunction
• Open or short circuit in the relay control circuit
• Blown air conditioning fuse
• Malfunction of the compressor clutch (coil, bearing)
• ECU malfunction (rare)

How to Fix

1. Check the A/C fuse and relay
2. Replace the relay with a known good one and check the operation of the air conditioner
3. Check the voltage at the relay control terminal with the air conditioner on
4. Check the voltage at the compressor clutch coil
5. Inspect the wiring and connectors of the relay and compressor clutch
6. If the clutch is faulty, replace the clutch or compressor assembly

Related codes

Error P0645 by Vehicle Brand