P0645 A/C clutch relay control circuit
What P0645 means
The engine control unit cannot properly switch the relay that engages the air-conditioning compressor clutch. The A/C may stop cooling or the compressor may stay engaged.
P0645 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 60–250 €
- Workshop time
- 0.3–1.2 h
- Repair difficulty
- Easy
- DIY possible
- Yes
- Check engine light
- Yes
- Affects emissions test
- No
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Air conditioning not cooling
- A/C compressor not engaging
- Compressor running constantly
- Check engine light on
Common causes
- Faulty A/C clutch relay
- Blown fuse
- Damaged wiring or connector in the relay circuit
- Shorted compressor clutch coil damaging the relay
Can I keep driving with P0645?
You can keep driving, but have it checked within one to two weeks. Only the air conditioning is affected.
What to check first
- Check the A/C fuses and relay
- Swap the relay with an identical one to test
- Check the relay control wire from the ECU
- Test the compressor clutch coil resistance
Related codes
- P0650 Malfunction indicator lamp (MIL) control circuit
- P0660 Intake manifold tuning valve control circuit/open (bank 1)
- P0628 Fuel pump A control circuit low
- P0627 Fuel pump control circuit/open
- P0620 Generator (alternator) control circuit
- P0670 Glow plug control module circuit/open
- P0615 Starter relay circuit
- P0610 Control module vehicle options error
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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