Thanks for the reply. I spent a good part of the day reading/re reading the FAQ section. It can get your head spinning there is so much info. I did the 'battery to compressor direct wire from reading the FAQ. The mistake I made was to not have the engine running at that time. The sound I got was very much like that of a relay clicking when hit with power. It was not loud nor forceful. I will do the test again in the afternoon and hopefully confirm the status of the compressor. I was working this after noon on accessing the PC board behind the control panel to take a good look at the solder spots to see if that is an issue. An idea as to which relay I would be looking for on the panel or will that be self evident when I see it? I have a spare panel from a late 70's 740, maybe it will have a same type relay to replace as part of the test. Failing that, is this something my local NAPA might be able to lay their hands on?