The A/C in my car works great but when it is on and I am at a stop the compressor makes a knocking sound that is loud inside the car. The sound goes away as soon as the rpms pick up. Any one know if this is normal? Any one know why it does this?
Even when it is making the noise the A/C is working fine.
Thanks[/align][/align]This is on a 1983 300SD with 190k miles.[/align]

 

This is a good place to use red Loc-Tite thread locker.

 

Checked last night and the belt is good but whips a little, the condensor fan is good and works as it should. Next is remove the belt and shake things to see if anything is loose then readjust.