[R129 SL] SL-500 Air conditioning

[mid-co at ix.netcom.com]

The air conditioning in my '95 SL 500 went from ice cold
to hot hot literally in a minute or two.  I've checked  fuses
# 7 and "B"  both meter fine.  Is there a relay I should 
look at ?  If I need a compressor , new , or rebuilt ??
the compressor seems to be 

I'd like to hear others experiences with their air
conditioning units. on these lovely cars

Thanks ....Bruce in Nashville