Possible causes

– Faulty Air Conditioning Clutch Relay
– Air Conditioning Clutch Relay harness is open or shorted
– Air Conditioning Clutch Relay circuit poor electrical connection

When is the code detected?

Code P0646 may be stored if an open or short exists in A/C clutch relay control circuit.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0646 BMW Description

A/C clutch relay may also be referred to as A/C compressor clutch relay. A/C clutch relay circuit is monitored when ignition is on and battery voltage is greater than 10.4 volts.