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My 1977 wipers are working one minute, then stop on their own without returning to rest stage. Then later they will return to rest stage when I try again. Then they won't start at all. Then they will start if I push the washer fluid button. Then they won't start and I get washer fluid leaking down to the garage floor. Then they budge slightly but won't move. And now the wiper motor makes a click noise when I work the wiper switch, but there is no motion at all. Is this a wiper gremlin or a dying motor or a weak ground? Thanks for any suggestions.
The clicking you are hearing is the Park Switch energizing you should hear that.
When you turn the wiper switch, high or low you are just switching the switch ground circuit, sounds like that is working correct.
There is a single motor case ground that needs to have a good path to ground.
There is a brass tab on the motor where that single ground wire connector plug's into (Red Arrow).
The starting point of that ground is on the starter side bell housing bolt, there will be a 3/8" eyelet and a black wire.
Check those areas for a nice secure connection.
My 77 wiper motor started acting up about 10 years ago. I checked all the wiring and switch first. all were good. So I thought what do I have to loose, it doesn't work anyway. So I pulled it apart. found old fashioned relay points in it like a early mechanical regulator or ign. breaker points. filed and cleaned these contact points. assembled the motor and it's been working fine ever since.
The clicking you are hearing is the Park Switch energizing you should hear that.
When you turn the wiper switch, high or low you are just switching the switch ground circuit, sounds like that is working correct.
There is a single motor case ground that needs to have a good path to ground.
There is a brass tab on the motor where that single ground wire connector plug's into (Red Arrow).
The starting point of that ground is on the starter side bell housing bolt, there will be a 3/8" eyelet and a black wire.
Check those areas for a nice secure connection.
Thank you, I just checked those two connections. The black wire is solidly connected on both ends. This model year doesn't have a wiper override switch under the dash, right? So should I test the motor next?
Last edited by Rick77white; May 5, 2021 at 06:57 PM.
You don't have to pull the motor to test it, but I would disconnect the wiper arm linkage with the single nut to motor first.
Just make sure the wiper motor is in the park position first before both disconnecting and reconnecting linkage.
The center Yellow wire on the 3 wire plug is 12vdc switched.
You will have to make some jumper wires for the ground, both to switch the motor from high-low speed and the motor case ground.
Do this check first and get back...
Bmotojoe, I tested the motor with jumpers and it worked perfectly, and looks nice and clean inside BTW. Then I tested it with the actual car wiring clipped on, but cover off, and again it worked perfectly. Then I attached the linkage with the bolt, and turned the switch, and it wouldn't budge. All I heard was that clicking sound. I unhooked the linkage, manipulated the wipers manually, reattached the linkage and it worked right finally. My best guess is the brass tab screw that goes through the cover and into the motor housing was loose and not doing its ground duty, despite the wire clip being tight on the tab. And maybe I tightened the linkage bracket too tight to cause that first non-start. What do you think?.
I know my motor will struggle a little if the glass is bone dry and it could have been that the blades were just stuck a little.
Could have been the motor ground lug being loose?
When you had the black cover off did you happen to look at the 20ohms resistor (shunt field black wire) for any unusual signs of overheating?
These original motors are pretty tough and unless the brushes completely wear away its usually the park switch contacts, relay coil or the resistor of the park switch.
I'm not suggesting to replace the switch just yet but you can find NOS switches on E-bay for $30.00 - $40.00 and are easy to change with minimal soldering skills.
GM #4960755
LINK:https://www.ebay.com/sch/i.html?_fro...60755&_sacat=0
If a new switch is in the future, Make sure the two small copper wires are separated from touching each other before you install.
These old switches have been bumped around, handled, something to look for.
The failure happened even if I soaked the windows, and I made sure the wiper arms weren't tangled. I didn't check for overheating evidence, I looked for cracked plastic and debris. The bolt that the linkage fits onto seems to have some wear. I will keep in mind that it might be the three-contact switch needing replacement. Thanks for the tip and advice. For now, it seems most likely to be the ground not making good contact through the fastener that screws into the motor housing. I tightened it as much as I dared while avoiding cracking the plastic cover. Time will tell.
If you think a extra ground jumper wire will help, use a couple crimp connector eyelets and a short length of wire, the screws a plenty long enough.
Also, there are lubrication pivot points that may need to be cleaned and re-lubricated.
Do one arm at a time marking the location of the lock nut and stud location first.
A small dab of white lithium grease will work on the pivot areas.
Great idea for the extra ground. The Wiper arms are very grimy, so I will clean and lubricate them. One question, there is supposed to be some wiggle in the linkage, right? I've seen that in videos. Thanks again for your help and sharing the photos.
In this photo you can kinda see the brass liners surrounding the pivot area under the slotted clamp brackets.
Same for other end of transmission arm but different style.
Well, sad to report my wipers stopped running again. This time I just wiggled the three-contact switch and it started working. Wiggling stops and starts it. It's not the wire contacts that are moving, but the whole blade unit. I wonder if it can be tightened, or must be replaced. I pulled out the switch unit and it's the park blade (top) that is loose. Can a screwdriver tighten the blade in the plastic housing enough to solve this? I can get a new switch unit as you pointed out, but I am not confident in my ability to solder the two wire connections well. Pics below
Last edited by Rick77white; May 13, 2021 at 02:13 PM.
Yes pull the cover, there is a second mounting screw securing the switch assembly to the motor body.
I think it is a 5/16" head maybe a 3/8", I don't remember off hand but it is larger than the cover screws.
Crazy wiper behavior - suggestions?
