The circuit boards GM used for the wiper motors in their later 1990s - early 2000 model trucks were tee-total pieces of *expletive deleted*it.
The board in my GMC began having issues within the first few months after I bought the truck new. The wipers wouldn't stop when I only wanted to wash off the windshield or they'd stop dead in the middle of a downpour whilst cruising along at highway speeds. The wiper issues were serviced by the dealership two or three times while under warranty. When they went back to acting up, once out of warranty, I replaced the board with an aftermarket part; from NAPA at that. I haven't had any problems since.
What exactly are you needing help with?
Locating the wiper motor/module? <-- If that's it, now granted I've never seen one on a van (I don't think many a human eye has...
), but I believe your thinking is correct; the whole wiper motor assembly is behind the dash. Wwaaay behind the dash. See if you can lay hands on a Haynes or Chilton manual for your van. One should have some decent instructions on getting to the wiper motor. The circuit board should be housed in the assembly for the motor, covered with a plastic cap and retained by three or four torx screws.
Good luck!
