I have an issue with the AC in my '91 740 turbo wagon. After reading a bunch of threads, I decided to try re-soldering the MCC board. I removed the MCC and melted the solder joints that I saw in the pics in another thread, and a few others where wires connected the board. It didn't look like any were cracked or loose. I didn't think new solder would fit on the joint without making a mess. Put the MCC back in and it still doesn't work. The compressor has recently been replaced, and I am pretty sure I have pressure, and the pressure switch has been checked and is OK. Where do I go from here?

 

you can jump the pressure switch with a paper clip.

with a test light (or multimeter), check for power at the clutch.

look on the back of the compressor. if there is a brass looking device that the wires go to before going to the clutch, that is a temp sensor that will keep the compressor from engaging.

if you have no pwer at the clutch, check both pins(to ground) at the pressure switch, one should have power. if you have no power there, your problem is much worse, unless you find a bad fuse.