1984 300d ac works good on highway but at idle sounds like a bunch of rocks in the compressor any ideas, maybe needs oil and how does one tell how much? Also the sight glass on the drier what should I see? I'm seeing bubbles at idle.
Thanx Jimmy

Normally, you use compressor oil to prevent the sound of rocks in there. That sound probably means that it's too late.

Some bubbles at idle is normal I think. My '91 had those when new, still has them, still cools great with good pressures.
Are you sure the sound is from the compressor? My tensioner mini-shock-absorber got loose on the bushing, knocked like crazy, but only when the compressor was on, creating more load on the belt. The load from the compressor will highlight bad idler pulleys, tensioners, etc; that quieten down when the compressor turns off.

DG