Repalced a AC compressor and found out it's bad ... diagnose help needed

[bennett]

Buddy froze up his ac compressor on his 85 300TD and we picked up another off a good wrecked 83. Installed the compressor and had it filled and got the call from the ac guys that the pump does not work. Th outfit doing the refill is a good reliable shop and knew about jumping the pins to engaged the compressor etc.

How does one go about testing and diagnosing a ac compressor to see if its good?
The replacement was out of a known runner and turned freely so we thought
it was ok... we have 2 more to replace it with... just wondered if someone can give us the heads up on telling which is good?

thanks from the "Do it Twice garage"

[funola]

If you spin the compressor by hand by palming the center (not the pulley) and put a finger over one port at a time, you should feel suction on one port and pressure on the other. That is very basic test but does not guarantee the compressor is up to sepc. If you get no suction or pressure, it is NG. Another you can do is plug one port and pressurize the other and see if it holds pressure. If it does not, it has a leak.