Windshield Wiper Problem

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1987 GMC Jimmy

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Hey, guys. I haven't posted in a few months busy with that Caprice, and I have a question that works for squares, too. If my windshield wipers are turned on, even for a second and immediately turned off, they will not stop running for several minutes. I'm guessing something's shorting out, and I'm dreading, however certain, that I have to crack open the steering column to clean contacts or something. Can someone help me out and give me further instructions?
 

chengny

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Have the hood open, turn the wipers on and switch them off. Then, while they are still running (and switched off), go to the wiper motor and disconnect the parking switch harness plug. That will be the plug with 2 leads that connects on the gear box:


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If you unplug it, and the motor stops - the problem is most likely in the parking switch. Another possibility is that one of the motor windings is shorted to ground. Either way, unless you have enough free time on your hands to rebuild the motor, you'll gonna have to buy a new one.

That's the bad news. The good news is; if you can stop the motor by disconnecting the parking circuit - that means the problem is isolated to the motor assembly. There is no short to ground in the control leads - between the motor and the switch in the column.

If the motor doesn't stop when you pull the parking switch plug, there is still a chance that one of the motor windings is grounded internally. To check that, pull the 3 lead plug from the main motor housing. Apply an external 12 VDC supply at the terminal that connects to the WHT lead. This supplies the common (positive) side of the motor windings. With the plug removed, the other two (negative) sides of the windings can't possibly be grounded via the factory wiring. So, only if an internal short to ground exists, can the motor run:


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If the motor doesn't run with power applied to terminal 19...the ground exists in the wiring of either the high or low speed control legs.
 

1987 GMC Jimmy

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This is all great information. Thank you so much.
 

1987 GMC Jimmy

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Have the hood open, turn the wipers on and switch them off. Then, while they are still running (and switched off), go to the wiper motor and disconnect the parking switch harness plug. That will be the plug with 2 leads that connects on the gear box:


You must be registered for see images attach


If you unplug it, and the motor stops - the problem is most likely in the parking switch. Another possibility is that one of the motor windings is shorted to ground. Either way, unless you have enough free time on your hands to rebuild the motor, you'll gonna have to buy a new one.

That's the bad news. The good news is; if you can stop the motor by disconnecting the parking circuit - that means the problem is isolated to the motor assembly. There is no short to ground in the control leads - between the motor and the switch in the column.

If the motor doesn't stop when you pull the parking switch plug, there is still a chance that one of the motor windings is grounded internally. To check that, pull the 3 lead plug from the main motor housing. Apply an external 12 VDC supply at the terminal that connects to the WHT lead. This supplies the common (positive) side of the motor windings. With the plug removed, the other two (negative) sides of the windings can't possibly be grounded via the factory wiring. So, only if an internal short to ground exists, can the motor run:


You must be registered for see images attach
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If the motor doesn't run with power applied to terminal 19...the ground exists in the wiring of either the high or low speed control legs.

Hey, the motor now stops on command. Loose connection (oops). However, it's nice and slow like they all get when they're old. You mentioned rebuilding it at home. What's involved there?
 

chengny

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Backing up for a minute. I should have asked this first:

How is your overall electric system? Are the alternator and battery in good condition? What does the dash voltmeter read at idle speed? If you revv the engine, does that seem to increase wiper motor speed?

If all those things are okay, go to the wiper diagnostic.

However, it's nice and slow like they all get when they're old. You mentioned rebuilding it at home. What's involved there?

Ahh...there's really not too much, but you'd have to be familiar with small DC motors. Also, you'd have to wing it - there are no rebuild procedures available, that I know of.

Unless you are extremely "thrifty" and have lots of time/patience, you probably don't want to rebuild that motor. Another issue is parts. If inspection/testing doesn't reveal any other obvious external problems, it's most likely the brushes that are to blame for the slower than normal operation But I don't know if replacement brushes are still available.

Last time I rebuilt a anything with brushes was about a year ago. It was a Bosch alternator. And while a complete voltage regulator assembly was available everywhere, the best price was like $90. I tried for a few days but I couldn't source just the brush set . Ended up buying some similar brushes from an old guy who was still running a auto electric repair shop. I had to file them down to make a custom fit with the rigging. But - he only charged me $5.

I wouldn't jump right to the motor just yet anyway. I would inspect the linkage and run the motor with no load, before tearing into a fairly involved motor repair.

Here are the first tests I would do.

1. Just pull the wiper arms forward until they are locked in the off-glass position. Then, with the arms/blades no longer in contact with the windshield, run the wipers at both speeds. Note whether they now operate at normal speed. If so, inspect/replace the wiper blades. If there is no noticeable increase in speed, do the next test:


2. Run the wipers without the transmission system connected to the motor output shaft. That will confirm/eliminate the transmission system as the problem. The "transmission" system is just a fancy term for the pivots and arms that connect the motor to the wiper arms.

You'll see different ways to disconnect the motor from the linkage.

The standard factory procedure involves removing the air inlet grille panel (AKA the wiper cowling) and the air inlet screen (the plastic strainer under the cowling) and accessing the ball joint through a slot in the steel frame of the cowling.


I just release the 3 mounting bolts. Then I pull the wiper motor body away from the wall - just enough to get a wrench on the motor shaft nut. There is plenty of play and flexibility in the linkage to allow the motor to be pulled out.

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With the motor separated from the wiper linkage, arms & blades, you can test run it and see if it runs any faster. You can also play around with the linkage - through the hole - and check it for loose joints or binding.

Make sure the motor is in the parked position when removing and re-installing the crank.

Also, if you use my method for removal, take note of the crank arm position when the motor is parked. It has to go back on in the same direction. The shaft and the hole in the crank arm have flat sides but they can still be 180 degrees off.
 
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87scotty

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this post helped me very much this am! I decided to change out my wiper motor (been broke for months) i was not about to tear off the air inlet off at 430 in the am
 

shiftpro

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Have the hood open, turn the wipers on and switch them off. Then, while they are still running (and switched off), go to the wiper motor and disconnect the parking switch harness plug. That will be the plug with 2 leads that connects on the gear box:


You must be registered for see images attach


If you unplug it, and the motor stops - the problem is most likely in the parking switch. Another possibility is that one of the motor windings is shorted to ground. Either way, unless you have enough free time on your hands to rebuild the motor, you'll gonna have to buy a new one.

That's the bad news. The good news is; if you can stop the motor by disconnecting the parking circuit - that means the problem is isolated to the motor assembly. There is no short to ground in the control leads - between the motor and the switch in the column.

If the motor doesn't stop when you pull the parking switch plug, there is still a chance that one of the motor windings is grounded internally. To check that, pull the 3 lead plug from the main motor housing. Apply an external 12 VDC supply at the terminal that connects to the WHT lead. This supplies the common (positive) side of the motor windings. With the plug removed, the other two (negative) sides of the windings can't possibly be grounded via the factory wiring. So, only if an internal short to ground exists, can the motor run:


You must be registered for see images attach
You must be registered for see images attach



If the motor doesn't run with power applied to terminal 19...the ground exists in the wiring of either the high or low speed control legs.

This is all awesome info Jerry. Where tf where you the other day haha? So, parking switch plug.. cool. I had to unplug mine to stop the pump from running. If you didn't see my posts from the other day, problem started when the pump wouldn't shut off. I kept trying by turning the wipers on and off and then they quit altogether. I had an interesting drive home in a thunderstorm after that. Driving by Braille almost. Next day I got my wipers working by bump starting them, but the pump just wouldn't stop until I pulled the plug.

I have to admit, the pump stopped priming the day before. I gave the tank a ******** to prime the pump and it was working perfect. The next day is when everything took a crap. The pump wasn't priming either (after the bump starting the wipers) but I thought I felt it vibrating so it got unplugged. I realize I didn't actually verify the pump wouldn't stop running... duh.

I have a fridge to unload (with a rare sore back) then I'll open the hood again. I'll plug that 'park' circuit back in and see wtf...

I don't have anything against buying a new motor from RAuto, even thought the process will end up costing me MUCH more than the price on the website... but these wipers worked awesome. Stronger and faster than my '86. Not the typical sluggish action from a 38 yr old truck. Oh well maybe less because it says reman on the motor.
 

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