Hi all, I am troubleshooting an issue with my 82' 300D:

Everything works for 5-15 minutes after the car starts, then the blower motor will not run unless the compressor is engaged. Low, high, or auto, motor will not respond.

I've done a lot of research, and looked into the typical suspects:
-Inspected/replaced fuses
-Checked blower motor, looks like it was replaced by PO this year
-Inspected PBU. No solders broken, but reflowed everything anyway
-Swapped out the resistor, temperature regulator, and fan relay box with multiple junkyard spares
-Soldered new capacitors into a temperature regulator

None of the above worked. Weirdly, if I unplug the temperature regulator (silver box) it fixes the problem, but I loose a bunch of functions of course.

Any ideas? Thanks all.