There is a bundle of wires that runs front to back, right through the middle of the driver's floor (I didn't read every post, so you may already know this) which does contain the wires for the tail lights, so you may be on to something.

 

Can u tell where u found the issues. Was it a bad group or wires shorted under the carpet

 

Leaking windshields, driver door seals or rotted floorboards can cause the wiring harness from the dash to the rear of the truck to sit in water and corrode. It is usually under the drivers carpet in the bottom of the foot well. When this happens there are usually multiple wonky behaviors in the back half of the truck and/or power seats.

George

 

Thank u very much George. Got a question, just bought this
blazer for my daughter, mint condition garage kept for the past twenty yrs. When I hit the brakes it cause the rear wiper to jolt just a little. No wet carpet. However, the hood is bent on both hinge points. I'm sure u know y and the elderly lady I bought it from confirmed her husband forgot to latch it and it blew up on him going down the Rd. I'm only assuming it may have cracked the windshield and they had it replaced. It's raining here alot and no wetness. But if ever got wet previous is there no drains in the floor pan and would u look for a ground issue or corroded wires in the floorpan first. Thanks for your time

 

There are a couple of different ways to go about this. We can analyze the circuits that are not acting right and attempt to confirm a short in that wiring bundle, we can inspect all the grounds for those circuits or if your convinced its the floor pan wiring, you can rip the carpet up. I'll help you with whatever approach you want to take. If you want to test and diagnose this start by listing everything that acts up.

George

 

Thanks again, I'm going to try and tackle this again tomorrow after work around 4pm Eastern. One more question I just realized while under the rear of the blazer it has a trailer wire pigtail that was stuffed in the frame. A mile of electrical tape around the aftermarket connection. Could this cause the same issue.

 

I just went back and looked at your original post. You will get continuity to ground on a lot of working power circuits with the power off because your just measuring the resistance through the load like light bulbs or motor windings so that alone does not tell you much. So are we trying to solve the original problem of parasitic battery drain or the fact that the brake light turns on the rear wiper motor?

George

 

Thanks again George for your time, much appreciated! The only issues is a faulty gas gauge fluttering and rear wiper jolts a little when break pedal is pushed. No battery drain.

 

The rear wiper doesn't move much. It just starts to move and resets but it does it Everytime the brake pedal is pushed.

 

Tom is right that those two systems share the same ground and he is also correct that wonky electrical problems can be caused by a bad ground but not likely to be the case here. Back feeding due to a bad ground requires multiple ground points like with parking brake and turn signal lamps. You lose one ground and the lamp being powered looks for the next best ground which is through another lamp to another ground point lighting them both up in the process.

Does this happen only while driving or does it happen in park in the driveway?

George