Are you absolutely sure it's not the wiring? Sometimes wires can corrode and/or break inside the insulation and you'll never find it just by looking at it, you have to pretty much ring out every wire to be sure but it could save you 500 big ones... I had major electrical problems on an EX200-2 Hitachi a few years ago and even though all the wiring looked good from the outside, it was all junk. Worked, then didn't work, then would sort of work, then quit for good... I ended up rewiring the entire machine and it works like new now. The fact that your aux. stopped working, then worked again, then stopped, especially after you were in there wiggling wires and stuff leads me to believe wiring is the culprit. I would ring out all the wires between the module and switches, module and coils and wherever else the wires for the aux circuit run just to eliminate that possibility.