Steve, you make a good point.
I looked up the specific compressor used on our CATs and located the manual for it. The same compressor is used on the C-7, C-9, C-13 engines). Of course there is always a possibility that "a member's engine" has something different.
I am emailing you the Service Manual for the Air Compressor used on our CAT engines. That manual also has a good description of how it works and a nice troubleshooting section.
BTW - the air compressor is CAT p/n 385-0936 (OEM# 255-4160) which is a single cylinder compressor. It is actually the Bendix BA-921.
Any member that wants to verify what parts are on their engine can go to
https://parts.cat.com/en/catcorp you need to register with the site, then put in your engine serial number.