B0640moderate severityBody
A/C Compressor Clutch Relay Circuit
on 2009 Audi A6 3.0L Supercharged V6 · AWD
What this code means
Malfunction in the A/C compressor clutch relay circuit. The relay controls engagement of the A/C compressor.
Symptoms
- A/C not blowing cold air
- Compressor clutch not engaging
- A/C works intermittently
- Relay clicking
Common causes
- Faulty A/C clutch relay
- Relay control circuit issue
- Low refrigerant triggering cutoff
- BCM or PCM relay driver failure
- Corroded relay socket
Diagnostic steps
- Check A/C clutch relay
- Test relay with jumper wire
- Check refrigerant pressure
- Test relay control signal from PCM/BCM
- Inspect relay socket for corrosion
Repair notes
Replace A/C clutch relay. If relay keeps failing, check compressor clutch current draw.
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