OBD-II code · Powertrain (generic)
P0645 A and C Clutch Relay Control Circuit
A general circuit fault on the A/C clutch relay control - the line over which the ECU engages the magnetic clutch to drive the A/C compressor.
Is it safe to drive with P0645?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOpen in relay or wiring
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.2 h
- Emissions test
- Usually unaffected
- Parts involved
- AC Clutch Relay
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.