they don't have clutches - most cars gave up the clunk and run flat out guzzeling fuel compressors, circa 2004
her 57 plate zetec climate has the modern variable rate compressor - this switches a valve on the gas flow silently cutting in, and the amount of engine power drawn flexes by a swash plate varying the compressor workload - based on temp setpoint, throttle position etc. - so hills, pulling away from rest, or hard acceleration winds back the AC to let the car make power....