A/C making noises
 

Air Conditioner making noises
I have a 1986 Mercedes 190e. As far as the a/c working. Works Great. But when I come to a stoplight and stopped in drive I get a rumbling / knocking type sound. Now at the stop light if I put the car in neutral. RPM raises alittle the noise lessens. If the RPM is 1000 or more I hear no noise at all.
It’s really hard to pinpoint where the noise is coming from. Maybe the fan clutch or possibly coming from the oil pan.
I do not see any real noticeable vibration or movement on the pulleys or belt.
Can someone tell me what my RPM should be with the A/C running, car stopped in drive.
Thanks for your help
Rick

The first thing I would check is the belt tensioner shock. On mine, the bushing at the alternator end wore out and made a rattling noise at idle. Replaced the shock and no more noise.

thanks I replaced the tensioner and shock damper problem corrected

Good news! And thanks for posting what fixed your problem, that's what makes this forum successful. Maybe someone with the same problem will do a search and find this thread.

Dave