I have a 1999 4 door 4x4 Blazer. The rear wiper worked last year but didn't work this year when I pulled the Blazer out of storage for the Michigan winter. I checked the fuse and it is fine. The wiper spray works fine too. I pulled the trim and removed the rear wiper motor. After playing with it for an hour I had it working. I put 12 volts/10 amps directly to the motor and reversed polarity on/off multiple times while tapping on the shaft that the wiper mounts on (this also included several blasts of WD-40). Eventually it broke free. I cleaned it up, greased the gears and ran it on 12 volts/40 amps for a few minutes to make sure everything was lubricated and working. Everything worked fine, the motor didn't heat up and I thought I was ready to claim victory. I put the motor assembly back into the rear lift gate, plugged in the wires, closed the lift gate/glass and attempted a trial run. The motor didn't work but I did hear a single click each time I toggled the switch from off to on. Any suggestions on what else to try?

 

I opened the wiper motor pulse board (contained in a black rectangular plastic case that mounts to the motor) and immediately sensed the smell of burnt electronics. I also found a burnt spot on the board. I have ordered a new board from Autozone and will pick it up tomorrow (non-stock item). I will post my results.

 

Well, I was bored and thought I would experiment with the rear wiper motor pulse board. As indicated earlier, I found a burnt spot on the board that disrupted continuity. I soldered it back together and checked it with my Fluke meter to ensure continuity. After reinstalling, I was glad to see the rear wiper work but it quickly became obvious that it wasn't right. There was only one speed and after turning it on, I could not turn it off without unplugging the power at the pulse board. Attached are pictures of the repair. This black box mounts on the wiper motor and can be removed without taking out the wiper motor. It looks like I will have to wait until the new part comes in tomorrow at Autozone.

 

The burnt out trace could have been a diode or possibly a chip of some sort. I've never gotten into the rear wiper setups on the s-series. I have repaired quite a few windshield wiper boards.

 

Alright- good news is the rear wiper is now working. The bad news is that I wasted time and money trying to save money. I thought that the pulse board was the only culprit but after buying and installing a new one, the wiper still didn't work properly. It moved but did strange things i.e. the arm/blade parked in intermittent mode but ran in the off position. I bought a reman'd motor, installed and it works fine now. I should have just bought the motor and pulse board as one assembly. This would have saved me a couple of dollars but more importantly a lot of time and a second trip.