I have a 1999 blazer and the rear wiper motor stopped working. I believe I have traced the problem down to a faulty ground.

When I disconnect the harness connector from the rear wiper motor and connect terminal C to ground I have 12 volts.

End gate & glass closed w/w switch to low ignition switch on B to ground I have 12 volts.

Connecting C to A zero volts.

When I reconnect everything and jump the ground wire from the logic box to ground the system functions as it should.

Does anybody know where the A black ground wire physically grounds itself? I am suspecting a problem there. I could also have a break some where in the harness.

Any help or suggestions would be much appreciated.

 

I did some more poking around and found a ground in the left rear next to the disconnect/connector for the left rear light assembly. When I check for continuity between the black ground (A) and the hard ground at that location there was none.

I suspected the ground wire would be broken in the area where the tail gate opens and closes. I removed the rubber flex shield that connects the gate to the body and protects the wire bundle. The black wire was broken.

I think this is a likely cause for a lot of rear wiper problems I have read about on this forum. During testing I found if the ground is partial and insufficient the motor will not operate and the logic box will make a buzzing sound.

 

Could be worse like my motor and killed itself, it would jitter in place and not move at all. I got lucky one day you pull-a-part and found a new remanned unit in a bravada for like $16. Worked great ever since.