Major DAD, It seems you have ruled out the usual suspects and as noted the problem is perplexing as it is the opposite of the normal complaint.
I am not HVAC knowledgeable, so I am assuming that the AC unit does not have a auto reset CB on the circuit from the panel to the unit and that is none inside the unit, so that leaves the line from the shoreline connection to the output of the transfer switch. That of course is assuming there is a transfer switch.
If you have a shoreline that has to be disconnected from the 30 amp outlet and connected to an outlet in the service bay, then the wiring from that outlet to the CB panel needs to be tested.
There is a guy on here that has Golden in his forum user name who is a really knowledgeable HVAC guy, in fact it is/was his profession. Try searching for him. Also Chris Bryant is an outstanding source of knowledge.
Good luck with your problem and sorry to read about the reason you downsized. It just so happens that we are doing the same thing for the same reasons.
