WHAT CAUSE A RATTLING SOUND WHEN YOU TURN ON YOUR AIR CONDITIONER on 2006 BMW 325i

wHEN I TURN ON MY AIR CONDITIONER YOU HEAR A RATTLING SOUND FOR THE OUTSIDE OF THE CAR. WHEN I TURN IT OFF THE NOISE STOP.

1 answer 1 comment
Thank you and well done for narrowing down the symptoms.
Does the noise sound from inside or outside of the car?
It could possibly be a noisy compressor or a power steering line rattle against one of several brackets, when the rpm rises as A/C is selected.
I have had other things causing rattles such as the tensioner and pulley assembly which was only heard with a/c on and applying slight load such as putting in D and turning the steering wheel.
Also possibly the A/C compressor tensioner and pulley assembly or the fuel vent line can also create a rattling types noise at a certain RPM.

Good luck
Hey, I am having a similar problem- but here is some more info. My AC makes a rattling noise (outside) when it is on and the car is in park or reverse. When I accelerate to a normal driving speed- there is no audible noise. It has become so bothersome that I turn the AC off when I pull up to a stop light because it is embarrassing. The air cools just fine though.