John & Alkraut,

Thanks for the information.

I have two 580's side by side in the garage, a 87 blue SL and a 88 Red SL.
The RED 560's ACC is the "cool" problem. The BLUE 560's Acc works wonderfully. With both autos running and engines warm I found the following!!!

RED MBZ BLUE MBZ

Top and bottom hose of monovalve Top and bottom HHOT
cool to the touch

Large Ac hose and metal valve ambient Metal valve ICE COLD
cool to the touch!!

Does this mean that the RED compressor is NOT "engaged? How do I manually or electrictly engage the compressor?

Thanks again for the HELP
Jim E
560 squared