Thanks to all for your inputs. Here's a status report.

It's not the ignition switch, but given the sypmtoms, could have easily been the case.

Thanks to Chuck, I've traced voltage from fuse #7 to the ACC terminal 12, left plug. You may recall earlier post of this problem indicated a blown #7 fuse first. Replaced fuse and unit ran successfully for something less than 10 miles before NOTHING operational.

So, I opened the ACC and started to trace the circuit from pin 12. Continuity from pin to "edge" solder joint good. So onto the next component solder "pad" in the circuit. Hmmmm, no continuity. Oh, there it is....an open trace in the circuit. Not blackened or seemingly catastrophic...just small piece of path missing. I've repaired the board but have not installed it to test.

I'm wondering if the blown fuse and then a blown circuit board trace indicate a load condition in some fan mode that creates too much load or appoaches a short when in automatic mode versus full on or low. Perhaps a faulty resistor bank, which should be readily evident and only impacts the circuit when running on a speed other than high or low? I think I'll dig into the blower compartment next, starting with disconnecting it and allowing the balance of the system to operate (monovalve, aux pump, etc. which should put some heat into the interior). Any other next step, troubleshooting thoughts?

Thanks to all for your suggestions. I appreciate your inputs.

__________________
Jim