GM Washer Motor Trouble

A vast majority of GM vehicles made between the 1960s-1990s use the same basic wiper-motor design. This consists of: (1) an electric motor to turn the wiper arms, (2) an electrical circuit to control how the assembly behaves, (3) an electric relay to engage a clutch that drives a mechanical washer fluid pump, (4) a wiper-delay circuit if equipped (it was an option).

Today these motor assemblies are no longer avaible new-old-stock unless you luck across one in the storage shelves of a dealer that has been in business for decades. Even the AC Delco models sold today are simply junk yard rebuilds. This means if you need to replace one you have to choose between a rebuilt model or pulling a used one out of a parts car. Regardless which way you do it this is a roll of the dice as most rebuilds, even the AC Delco ones, are done cheaply in 3rd world countries and are not reliable.

This page describes some of the common failure points in these motors and what you can do about them.

 

Wipers do not "park" after use

Wipers do not function at all

Washer fluid does not pump

 

Wipers do not "park" after use


The most common problem associated with these motors is that there will come a day when your wipers will not "park"park" properly after use. The wipers will function fine but when you turn them off they will keep wiping until your turn your car off. Then sometimes, but not always, the wipers will "park" once you turn the ignition switch from the off to on position.

This problem is caused by the park-switch failing. A mechanical-electrical switch tells the motor to park the wiper blades, but over time the switch wears until it no longer works. It is possible to rebuild these motor assemblies yourself and virtually every part of them can be purchased by AC Delco or numerous other parts companies. But that is probably above the skill-level and patience of many mechanics and consumers.

That means you're replacing the whole unit. You can go to a junkyard and start pulling them, but expect most of the junk yard motors to be bad in one way or another. The plus side is that junk yard wiper motors are inexpensive. Alternatively you can buy a rebuilt model from AC Delco or CarDone, but chances are you'll be out hundred(s) of dollars and get a unit that still has problems. On the plus side, rebuilt units carry a warranty so you can just return them until you get one that works. How long it will work after that is anyone's guess.

 

Wipers do not function at all

Sometimes your wiper motor will function at all. Meaning no fluid pumping, no wiper arm movement. There may or may not be an audible relay-type clicking sound when you try to turn them on. This is usually due to insufficient grounds on the wiper motor. The solution is to add new grounds between the metal-housing of the motor assembly and your firewall. You may need multiple ground straps running to multiple locations before the motor will function again. Be sure to scrape the paint off wherever the ground strap will be bolted to ensure a solid electrical connection. A star-washer (looks like a tiny mechanical gear) between the bolt and the firewall sheet metal improves electrical contact.

If your wiper motor assembly still does not function, and it does not function when tried in another vehicle, its dead and needs to be rebuilt or replaced.

 

Washer fluid does not pump

If the washer fluid does not pump you need to rule out the following first: (1) there is fluid in the washer fluid tank, (2) the inlet inside the tank is not clogged with dirt or debris, (3) the hoses and nozzles are not clogged anywhere.

If the washer fluid still does not pump, but the wiper arms function properly, the problem likely lies with the clutch mechanism for the pump or the pump itself. This will require taking the motor assembly apart and troubleshooting it, which is beyond the skill level or patience of most mechanics and consumers. So you're looking at replacing the wiper motor assembly.

But wait, there's more! Sometimes you cannot source a functional wiper motor assembly. You've gone through numerious rebuilt models and they were all bad in one way or another and now you are not looking forward to replacing an otherwise perfect wiper motor with another rebuilt one that may come dead in the box. So what-do-you-do???

Luckily GM has anticipated this exact same scenario! These wiper motor assemblies are such a pain in the butt that they carry an AC Delco washer pump by-pass kit.

Pump Bipass Diagram

 

The kit is AC Delco part number 8-6700 or 89001112 which can be had for under $20, but you may need to order it (don't expect it to be in stock near by). The kit does not tell you exactly how to use it, since it assumes a mechanic is the one doing the installation. The proper electrical connection is as follows:

1- Find the triangular connector on the wiper-motor assembly (as looking at it mounted to the car, it will be the connector closest to the passenger side).

2- Spice the top-left wire of this connector and connect it to the white (aka positive) wire of the bipass pump.

3- Spice the top-right wire of this connector and connect it to the black (aka negative) wire of the bipass pump.

Next, you should not use the cheesy plastic hose-T fitting the kit supplies and go to an automotive parts store and purchase a real brass fitting (you'll thank me later). You also may need a longer section of hose than what the kit supplies depending on where you mounted the bipass pump (I put mine on the plastic inner-fender) right next to the washer fluid tank.

This bipass pump is far more powerful than the one that is built into the original wiper-motor assembly, so there will be plenty of squirting action when you call for it.

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