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ElectricalSeverity Low: usually safe to drive

P0645A/C Clutch Relay Control Circuit

What it means

The ECU sees a fault in the circuit that switches the air conditioning compressor clutch relay.

Symptoms

  • Air conditioning not cooling

Common causes

  • Faulty relay
  • Wiring fault
  • Faulty compressor clutch coil

What to check first

  1. Check the relay and fuse
  2. Command the clutch and check for voltage at the compressor
  3. Measure the clutch coil resistance
Can I drive with P0645? Usually yes. P0645 rarely affects how the car drives, but it keeps the check engine light on and can fail an emissions test.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

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P0645: questions and answers

What does P0645 mean?

P0645: A/C Clutch Relay Control Circuit. The ECU sees a fault in the circuit that switches the air conditioning compressor clutch relay.

What are the symptoms of P0645?

Air conditioning not cooling.

What causes P0645?

Faulty relay. Wiring fault. Faulty compressor clutch coil.

How do you diagnose P0645?

1. Check the relay and fuse 2. Command the clutch and check for voltage at the compressor 3. Measure the clutch coil resistance

Can I drive with P0645?

Usually yes. P0645 rarely affects how the car drives, but it keeps the check engine light on and can fail an emissions test.