The AC/coolant loss may have only be related in that it's really hot and the extra heat leads to extra pressure on the cooling system.

The fluid loss was somewhat aft of the firewall. I think it was exiting through the drain tube located in the vestigial drive tunnel. Clearance is so low it's hard to be clear w/o lifting the car.

Because of the difficulty in replacing the junction block, my heater hoses have been macgyvered (bypassed) for a while. I found a tiny split in the bypass hose which might have been the source of my coolant loss.

Upon removal, I found an old crack in the original junction block, which explains my rapid fluid loss back in the spring.

I restored the system properly yesterday with a new junction block. After refill, did not seem to be loosing coolant any longer. I need to check it again today. More time/testing is needed. I'm tracking multiple problems simultaneously.

Thanks for the help.