P0645
Book Code P0645 Inspection
Automotive Climate Control
Low / Normal Under Shade
Code P0645 - A/C Clutch Relay Control Circuit Malfunction
PCM detected an open circuit, short, or impedance failure in the control circuit of the A/C compressor clutch relay.
Safe to Drive? ✅ Yes, Safe
Estimated Repair Cost 50 - 300 SAR
Common Makes Generic, Ford, GM, Chrysler, Jeep, Dodge
System Category relay
Symptoms of Trouble Code P0645:
- ⚠️ A/C compressor clutch never clicks or engages
- ⚠️ Only warm blower air from vents
- ⚠️ Code P0645 stored in PCM
Common Causes Behind Code P0645:
- 🔍 Burnt A/C clutch relay in underhood fuse box (70% of occurrences)
- 🔍 Blown A/C compressor fuse
- 🔍 Shorted magnetic clutch field coil drawing excessive amperage
- 🔍 Open control wire from engine PCM
Diagnostic Procedure Recommended by Auto Save Technicians:
- 1 Locate AC clutch relay in fuse box and swap with identical relay (e.g. horn relay) to test
- 2 Check AC fuse for continuity
- 3 Measure compressor clutch coil resistance (should read 3.0 to 4.5 ohms)
Specialist Recommendation:
Request Parts & Repair Quote
Try swapping the AC relay with your horn relay in the fuse box; it may fix it instantly!
Associated Components: A/C Relay A/C Fuse Clutch Field Coil
Frequently Asked Questions: Code P0645
Can I test the AC relay myself at home?
Yes, locate the fuse box and swap the AC relay with an identical relay (like horn) to see if the compressor engages.