this happened on my 97 wagon and i had to replace a bunch of wires from the hatch harness
heres a super simple way to do it.
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Tools Required:
Multimeter
Wire Stripper
Wire Coat Hanger or solid welding wire
Electrical Tape
about 30-40 feet of wire. i used red and yellow wire
lots of butt splices
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TAKE PICTURES TAKE PICTURES TAKE PICTURES TAKE PICTURES
Pull out all of the trim near the hatch. (on 97 outbacks you have to start pulling the trim at the front and work to the back. only the upper trim)
find the point on the inner hatch where the wiring harness splits into its different connecters. add a few inches and cut it
do the same for the body connecters down by the right rear fender. they should go up by the tail light and go into the hatch (use your multimeter to check if your not sure
now pull the new wire through with that fancy weldingwire/coathanger. i had 9 wires in my 97 the upper brake light connecter doesnt go into the lock area of the hatch. it takes a sharp left as soon as it goes through the boot and goes directly to the brake light. the ground from the brake light went up into the lock area and connected to the main ground wire from the body.
now for the hardest part. wire it up. I used a multimeter to check what wires went into the harness and then spliced matching colors. this worked for me just fine.
now put the battery on and make sure you dont get any BIG sparks. like the scary ones. (do this with your door closes and all the knobs set to off pop it on again and walk around the car and make sure theres no hot electric smells.
start the car and profit. it took me 2 days to do the entire procedure and i have no experience working with electrical stuffs