FIXED!!
I found the solution to my A/C problem on my '92 Olds 88 and you're not going to believe how I fixed it!
The symptom I was having was that the compressor wasn't getting a 12V signal. All the relays, swithches, etc. checked out so I had narrowed it down to either the A/C control module (in-dash), Heater & A/C Programmer, or the PCM - all expensive parts to replace.
I did a little digging on the 'net and came across the following tech tip (
http://www.asashop.org/autoinc/june99/techtips.htm). It's a good explanation of the GM electronic A/C systems like the one used on the '92 Olds 88. It also explains that if the compressor short-cycles for some reason, the system will fault and lock out the compressor until the problem is fixed and the faults are cleared.
To clear the faults & reset the PCM and Programmer you DISCONNECT THE -VE BATTERY CABLE AND TURN ON THE LIGHTS FOR ABOUT 10 SECONDS. I did this and my A/C now works! Much cheaper than the $600 in parts & labour I was quoted to change out the programmer - and this was the solution after $200 of diagnosis. I'll be stopping by the shop tomorrow to pass this info on to my mechanic. Generally he does good work but he sure missed the mark on this one.
I hope this info is helpful to someone else.