P0647A/C Clutch Relay Control Circuit High
- Generic OBD-II code · Powertrain
- How the car detects it
- The engine module switches the A/C compressor clutch relay through a low-side driver once the climate control requests cooling. P0647 means the voltage at the control output stays too high while the driver switches on (it should pull to ground) – the control wire is shorted to voltage; the driver shuts off for protection and the relay does not pull in, so there is no cooling. GM Europe's 2011 Saab 9-5 uses P0647 only for a short to voltage (check: less than 0.3 V on the control wire with ignition on and the module unplugged); Saab's EDC16 diesels use it for an open circuit instead (0.6 s). Not emission relevant; usually stored without the check engine light.
- What you may notice
- A/C not cooling
- Compressor clutch never engages
- Code stored, check engine light usually off
- Likely causes
- LikelyControl wire shorted to a supply wire (chafing)
- PossibleRelay with internal short (coil bypassed, very low resistance)
- RareWrong relay fitted
- RareOutput driver in the module faulty
- Repair
- Easy · Often possible to do yourself.Typical cost: €15 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.