Testing A/C Refrigerant

My situation is that my A/C isn't working. Appears the compressor isn't working.

I've read multiple times that you can't really go by the static pressure readings when the A/C isn't running.

So here's my question; If I can't get running pressure reading how do I go about troubleshooting exactly what the problem is. I can assume the compressor but that's just a guess.

 

you have to get the compressor working before you can do anything with refrigerant
so:
a) is the clutch working on the compressor, it should be audible with the hood up between the click and the load on the engine
b1) you get the clutch click but no change in engine load, the compressor is probably destroyed in side
b2) you get a click and a heavy load change, compressor is jammed with shrapnel or to much refrigerant so there is liquid in the compressor

 

It's possible you have a refrigerant leak which may be affecting the compressor engaging or not. Typically I'd evacuate the lines and vacuum test it to rule that out.

 

Take it to a shop. They have the proper equipment to test the system.

 

Thanks for the replies. It seems like the clutch may be a problem. The pully is turning but about every few minutes it starts to make a chattering noise then stops. This happens with or without having the AC turned on.

I was trying to avoid the high shop charges but maybe I can just start by asking them to do an initial assessment. But from the various posts on here it always seems like the shops either don't want to give an estimate based on actual testing or jump right to saying you got a bad compressor.

 

well check that the electrical connections are clean and tight

 

Reach down and try to turn the compressor hub with the engine off, if you can't turn it it's bad, if you can then further diagnosis will be required.

 

Thanks all for the comments will be looking into this further in the next while.