I am trying to determine whether my compressor is bad or under/overcharged. I have an older gauge but it tells me it has a good charge, the AC blows cold and works fairly well all around except for the fact that it knocks. In idle it doesn't knock as bad, but still very noticeable. When I'm driving and especially going through gear one it vibrates 10x worse than it does idling. Turn the Ac off and it is normal and drive as it should. I am leaning toward just replacing the compressor, but has anyone else had weird vibrations come from the compressor and maybe just had a charge issue?

 

what are the high and low pressures ? If your gauge only does low side pressure you really just guessing .

also pressure is relative to outside temp, search r134a pressure chart on google

 

That is utterly strange. Have you checked the belt for proper fitment?

 

Is the compressor properly mounted snug with all 4 bolts? Since it only does it with the A/C engaged it is likely not an issue with the pulleys. Have you checked the fans are mounted properly and aren't wobbling? I had a fan motor go bad this year that vibrated like hell.

I honestly would stop using the A/C before it grenades itself and you gotta replace the evaporator, condenser, expansion valve and receiver drier. I mean, if it hasn't already shed metal through the system.

For what it's worth I've never had a compressor knock on over or undercharge. They just cycle on/off or blow the blowout plug/valve. It sounds like you're playing with fire right now honestly.

 

I'm reading 2 issues

1. knocking
2. vibrations

Need video to see what is 'knocking'.

As for vibrations either your motor mounts and torque mounts need to be replaced or the compressor is just having a bad day.