AC compressor not cutting in
 

Merc 84 300D turbo.
Blower motor is ok, freon pressure ok, ac power switch ok, what else should I check to find out why the AC compressor is not cutting in

You can remove the panel under the glove box and check the "etr switch" located to the left of the expansion valve. Check to see if you have power to the switch and across the terminals. ALSO, with the a/c on try reving up the engine by snapping the throttle above 2500 rpm and see if the clutch kicks in, sometimes the clutches on the r-4 compressors get weak.

Clutch
 

Sounds like you need a clutch for the A/C compressor. Although it could be a lot of things.

But I would say the $40-50 clutch is bad. Order it through fast lane.

Have Fun!