Parked in the driveway.

 

OK. Yes the trailer wiring can be involved but that's easy enough to rule out. Pull the 4 trailer fuses and see if the problem goes away.


George

 

Hey George, I had to work till 8 tonight. My time is so limited right now but I did check a couple things on the blazer. I removed the trailer fuses and made no difference. However, when I remove the fuse for the wiper motor it stops doing. My thinking is that without the power circuit complete since I removed the fuse it's either a ground or the power wire to the logic control for the wiper motor shorted to the brake light power wire. Your thoughts are greatly appreciated.

 

I think its time to rule out a bad ground. You need to locate that G404 ground point, make sure its clean and tight and if that's OK then do some testing to make sure that you don't have excessive resistance to that ground point from the ground side of the brake lights (black wires). First order check is resistance with everything off. Best check is looking for a ground lift by measuring the low side bulb voltage to battery ground when the brake lights are applied. Do the brake lights have normal brightness?

If all of that is OK then yes the brake lights may be exciting the logic input to the wiper motor. Does the washer pump also engage? Probably the easiest way to check this is pull the wiring boot back between the door and body and pierce each of the two wires (dark green and white) in turn and see if you get a change in voltage with the brakes applied.

George