ac compressor makes chattering noise with engine off

[mr.vang]

with the key on the ON position and the ac button pressed, the ac compressor is making some kind of chattering noise. how can this be when the engine is not even running. i have never experience this before even with my previous 318i and other cars.

[jlevie]

That sounds like a problem with compressor clutch or it's circuit.

[mr.vang]

just found the problem, i installed a set of euro bumper earlier this week and today i notice the fan was rubbing against the valance, making the noise. after i pulled the valance out a bit and the noise is gone.