Hey guys! First post!

I little bit of a introduction. I'm Chris. I'm 21 and I am sort of the "Mechanic" at my parent's farm in southeastern British Columbia.

Because me and my brother drive 75km to and from school, we need a winter vehicle for when the roads are really crappy. My parents last fall filled those needs with a 1998 Chevy Blazer. It's a nice clean vehicle (175,000km), but it's not without it's problems, and that is why I am here.

This blazer is "Fully loaded" with a automatic tranny, a/c, power windows, mirrors and locks, and a 4.3L V6.

The one problem I am having trouble with the most is the rear wiper. When the switch is on, it wiggles on it's little brace, then when the switch is off, it breaks free and does it's job. Some reflexes and timing with the switch (In other words: Rapidly turning it on and off) inturrupts the cycle enough to turn off the wiper.

I don't know enough about the electrical systems to take a guess (It sounds like a pulse board problem, but the black box on the motor is a relay, and I can't really see a relay being the source of the problem.... uh, right?)

A little help? I'm really confused right now, and I would like some help getting out of this rut!

 

*Bump*

 

Because I'm not getting any input (Hint-hint?) I went and replaced the relay that rides on the motor. No change in behavior. I took apart the dash switch and cleaned the contacts. still nothing.

My haynes manual has nothing on the circut for the rear wiper. can I have some help?

 

never saw one do this but...you've already done some stuff...here is some more stuff I would do. Pull the upholstery off the tailgate and unplug the motor and see if you have 12 v to the motor when you command it on-keeping in mind when you turn it off it make continue to have 12v to it until it makes three or so finishing 'sweeps'. My thought at the moment is an issue with the motor but I'd do the above first and this may direct us(you) somewhere. Let us know! Jerry PS sorry about the delay in answering but most of us work and this is a free service so....anywho.....[:'(]

 

Thanks for the suggestion!

I just did some testing on the plug. The wire colors of the plug going to the motor are set up as

With one prong in the plug while the other on the back window latch (for a ground).
I noted that:
-the green wire has 0.05 volts when off, and 0.07 volts when on
-the orange wire always has 12 volts
-the white wire has 12 volts when on both high and low.
-the black is the ground (It checks out for continuity)

The motor gearbox looks like it has leaked some grease and the boltheads are touched with a bit of corrosion, but it's overall appearence is okay.

 

Well, I've got a similar problem... good to know I'm not the only one...

Normally, the rear wipers work perfectly. It's just after shutting off the vehicle, and opening the door (when the accessories, radio, etc. shuts off)... If the wiper switch is left on "lo" speed, the wiper motor will suddenly turn on "hi" speed, and keep running until the switch is turned "off". You turn the switch back to "lo", nothing happens.

This only happens when the vehicle is turned off and the wiper switch is in "lo" when opening the door... Switch "off" or "hi"... nothing. And it only happens after opening the door, not before.

Oh, I guess I should mention I replaced the wiper motor a couple of months ago (just wore out), but haven't noticed this problem until recently.

Any ideas? I'm baffled...

 

I've got a concern about the module that runs piggyback on the motor but I'd hate to throw parts at it. marklar-got no idea what year your is from the info shown and I haven't time to search thru any previous threads. Jerry

 

maklar, in your case, it sounds like the wiper is not going to its park position if left on when the key is turned off, then it is trying to get there after RAP is turned off (opening the doors). This should happen when the key is turned off...

Here is the schematic. It would seem that all of the controls, aside from the switch, lie in the motor itself..?



I guess it is possible that somehow the power wire to the switch is getting power after the truck is shut off. You can check this by testing for voltage at the RR WPR fuse. It should only have power when the ignition is on (ACCY or RUN).

 

That's the part I replaced, and still no behaviour change.

swartlkk, thanks for the diagram!

 

Another common Blazer problem: failure of the rear wiper. <sigh>

Not to be a spoilsport or anything, but I replaced mine when it had the same problem, and the replacement didn`t work either. My solution?

I removed the entire assembly and coat the rear windshield with Rain-X after each wash. Rear wiper is now no longer necessary. I also found that it just plain looks better. However, I still need to get the holes filled and the hatch painted. I wanted to get the hatch painted anyway, because of some flaws I found when I shaved the Chevy emblems. It seems at the factory they don`t wait for the paint to dry before applying the daggone things.

To prevent water from getting into the holes, I just used some black heat-resistant tape along the inside of the hatch to cover it. It`s been like that for several months and has not come loose. Just temporary until I get the paint job done.

(Side note: I do plan to update my signature soon, because it doesn`t show the shaved rear wiper or the new fog lamps.)