Leaderboard

Hopefully it's just the motor. Remove the plastic cover inside of the rear hatch, unplug the motor, and see if the wiper switch still pops the fuse. If it doesn't, then it's probably the motor, though I would test the motor before replacing it on the off chance unplugging it just broke the circuit to some other faulty component. If the fuse pops without the motor, or the motor tests good, you'll have to do some digging. EL-69 of the '90 manual (free download from cardiagn.com) shows the whole circuit. EL-90 has component locations, EL-93 and up should help you find the relevant connectors. By disconnecting those, you can narrow down where the problem is. If the fuse doesn't pop anymore with 13B disconnected, then you know the problem is in the hatch. If it still pops with 297M disconnected, you know the problem is between 297M and the dashboard. You could unplug the amp and/or relay. IIRC they're behind the lower trim, left of the rear cargo area. If unplugging one saves the fuse, either that component or something downstream is bad. This approach should narrow stuff down so you're not screwing around chasing wires at the wrong end of the truck. If you can't be arsed to do all that, or your troubleshooting leads you to the rear hatch harness, check the wiring between the body and the hatch. That's the only place in the circuit where wires have to flex, so that's where I would expect the wiring to fall apart first.