Thanks Arthur. Disconnect at pigtail stopped the fan so failure points to the blue relay. Is this a solder joint issue that possibly can be fixed or do I just buy a new one?

BTW I understand your caution about the 20 PSI variance betw. reading on gauge versus the pressure at switch. I am undercharged and high side was at 240 PSI @ 82*F and 70% humidity so I was not close to triggering the aux fans.

Jack