[65trucks]

I kind of ran into the same issue the other day, even though yours may have a different cause. I put a new instrument panel bezel in with a new gauge panel. Put everything back together and tried everything, but the wipers. So heading to the local cruise in a few days later, it starts to rain. Wipers don't work, at all. I wiggle wires, do everything to try to get it to work. Nothing.

So I did not know the switch grounds thru the new, painted, black, bezel I have. The way I tested it was to turn the switch on, with ignition on, and ran a fused jumper wire to ground. Wipers started working immediately. Took a piece of sandpaper on the back side of the bezel where the switch mounts, and bolted it back up. Works like a charm. Something to check on while you are trying to find a cure.