Hi all, this if my first post here and I'm stumped.

My 2014 Express 1500 cargo van with 139k miles dies immediately when the wipers turned on and will not start until they're turned off. The first time I try to start it with the wipers off after it stalls, it'll start, run for a couple seconds, then stall. After that it starts and runs normally as long as the wipers stay off. If I disconnect the harness from the wiper motor, the car won't start at all.

At first it only did this when the wipers were turned to high, but now it will stall at any wiper level. So far, I've replaced the battery (new one tests good), replaced the turn signal/wiper stalk on the steering column, checked all fuses and fuse boxes, and checked and cleaned every ground I can find. I'm thinking this is a short somewhere rather than alternator because it doesn't bog down (with AC, radio, windows, whatever), but instantly cuts out with the wiper switch.

This used to be a SafeLite work van and I'm sure they modified some things (removing the cast iron glue heater tied into the radiator lines was fun...), but no idea what would cause this. If anyone knows what could possibly be causing the issue, or how ability of the car to run could be tied to the wiper motor, or any steps at all for diagnosing, l would greatly appreciate advice.

This is a heavy vehicle and suddenly losing power brakes and steering on the highway in the rain because I tried to use the wipers was pretty nerve wracking...