Have shovel, will dig self a hole.
I'm now not sure if the AC clutching is a return signal issue or the solid state relay on its last legs (they are undersized). The clutch has a large air gap. A regular 40A relay with diode, might be clever.
Backprobed pins 1 & 2 of the three-way fan controller plug for DC voltage; 1 was V(bat) while 2 was 0.7V, seeming steady.