I have been trying to troubleshoot the A/C on my 1985 300TD. I have been told that the compressors are cheap and often seize.

My compressor is rotating with the engine belt, but it seems like the clutch does not seem to be engaging. I can spin the clutch disc easily by hand. Could this be a switch problem? If the compressor is seized would I be able to spin the clutch?

Help.