so i purchased a wiper hatch from a friend awhile back for my 87 s4, obviously i quickly found out that my car did not come with the wiring harness that could power the wiper. Since then i have been on a mission to find a body harness to plug and play so i can have a rear wiper. First i found one and pulled it, junk yard wanted $150 for it, i dropped it and walked out. Then i found one in an s5 recently, i was aware that it may not work because of all the differences between s4 and s5 but it was a gamble and it was only 30 bucks. It didn't work... then this past weekend i found an s4 gxl that had a wiper hatch, i pulled the harness and i installed it today. This is where things get interesting, i swapped them and plugged everything up on the new harness. re-apply power and my gauge lights, overhead light, and front parking lights come on... the switch is set to off. on top of that my brake pedal now operates my horn WTF! so i unplug the new harness one connector at a time to see what is causing this, low and behold, my existing dash harness is now causing it. what could have caused this? could plugging this different harness into the car have fried the cpu that controls the horn, lights, etc? i'm posting this and then going outside to plug my original harness back in, praying that it will fix everything

edit: also the car will not start, i've thought about the possiblity that the pinout just isnt the same on the harnesses, but it doesnt make any sense, they're the same year just different trim levels. why go through that trouble, i dont know any suggestions are welcome.

 

different BCMs is my guess ,, go back to the old harness and just wire the stupid wiper from its own dedicated switch and relay,, not all that hard to make it 2 speed either

 

haha silly mazda put two identical 20 pin connectors 3 inches from each other under the dash, i just had them reversed... go me.

 

heh,,Hope that worked for ya!