Those who have debugged their wiper motor electrical system, maybe you can help me.

- I have a 1980 corvette, I have replaced the dash & engine harnesses and the battery is fully charged & wiper fuse is new.
- I'm assuming that when the ignition is on ACC that I should have 12v at the middle plug of the 3-prong wiper plug - I don't
- I suspected that the wiper delay timer module was the culprit so I bought Lectric Limited's bypass plug:



I verified that there is 12v at pin 3 (brown w/ white stripe) which loops the voltage on to pin 2 (white wire) and verified that it is 12v.

According to the diagram, the white wire goes to the main terminal block in the firewall and across to the identical pin on the engine harness and straight to the middle pin of wiper motor plug (filled in w/ RED in pic below) and also down to the washer motor.



Problem is that there is no 12v on the middle plug and I don't know how else to probe it at this point. I can't probe the main firewall connector and I'm assuming Lectric Limited's harness'es are not the culprit. I'm assuming that the wiper switch has nothing to do with this issue since it doesn't have 12v going to it. Anybody have any ideas on how to debug this ?

Richard

 

I agree you should have 12 volts at center plug. Are you sure you should have it in acc position and not on position? I have what you call needle points that go on my meter leads. You can make home made one with a stick pin or sewing needle you use the needle to probe insulation on wire at points that wire is not on connector. You should be able to read at jumper inside then firewall connector and also at plug on wiper. Do you have ground at wiper motor aor what are you using for ground

 

Thanks henrikse for responding,

With ignition off, I move the key clock-wise one position, so actually its the ON position. I forgot the ACC position is actually backwards.

I do have needle points on my meter leads.

For the voltage reading at the middle connector, I put my meter ground on the alternator ground and the meter hot on the middle wiper spade.

I like the idea of probing with sewing needle on engine side of main connector, I'll try that. Is it true that the wiper switch should have nothing to do with this issue ?

Richard

 

I would agree the 12 volts comes from ignition thru fuse to brown white and you have a jumper to white so 12 volts should be there

 

YES...the ignition key needs to be turned to the ON position and NOT the ACC position due to you can not drive the car with the the ignition switch in the ACC position.....obviously.

So I gather you DO HAVE 12 volts on the white wire now???

Is it working now???

DUB

 

Hi DUB,

At the time you asked, the answer was no. But, I grabbed the old harness, and traced the white wire through the dash side into the engine side of the main firewall connector to find which position on the new connector I was dealing with. I then attempted to use a a needle to probe the wire but my leather needle was too large and the smaller ones just broke off. So I decided to unbolt the main connector, which was not an easy task, given its buried under the power brake booster. My intent was to "ring" out each segment individually. This is what I found:



If you look real close, you will see the bottom three spades are flat against the plastic sidewall. Evidently, they were out of alignment when I plugged in the connector and then when I bolted it together, it just splayed them aside.

Anyways, re-aligning them and bolting it back together fixed the issue with the 12v on the wiper motor & washer motor.

Turns out washer works, wiper motor does not, did a continuity check on the switch and it fails certain tests, so I'll have to order a new one.

Richard

 

Richard,

What tests did you perform on the switch???

Generally I check the 3 wire black connector that plugs into eh wiper motor where the center wire is the 12 volts you need to have when you turn your ignition key ON.

Then I verify that the housing of the wiper motor is GROUNDED......then I check the outer two terminals in that 3 wire connector and see if they are switching grounds when I move my wiper switch. This will confirm if you need to go but a new switch or not.

Have you attempted to 'bench test' the wiper motor while it is still in the car?? Before you go and buy a new one.

PM me if you need to....it is up to you.

DUB

 

Hi DUB,

- I checked for 12v on the middle connector and there was none (which was caused by the main connector spades being bent). Ok now...
- I then verified that the motor was grounded correctly.
- I did bench test the wiper motor using the actual battery and all it did was click so I purchased a new wiper motor from Lectric Limited (they specifically said to not bench test their new motor, and its under a 1 year warranty, and they do not carry the China built one that everyone is having issues with).
- The last thing I did was remove the wiper switch and bench test according to Willcox's test sequence:
(good) F is the pink wire, and the only time this wire will ping continuity to ground is when you push inward on the switch
(good) C is the purple wire.. If you test continuity from the purple to E, the black terminal you should have continuity in all positions except off.
(Failed) D Gray with a black stripe. This is your high speed ground and should pass continuity to the black wire connection E in all positions except Hi speed.

I'll check "the outer two terminals in that 3 wire connector and see if they are switching grounds when I move my wiper switch" tonight when I get home before ordering a new switch. May I ask how you are able to check these grounds when the connector is attached to the switch or do you bench test the 3-wire ?

Richard

 

Have the wiper switch plugged in and test the outer two wires to make sure that you can get a ground on one outer terminal ONLY when the switch is in PARK.. So that means the OTHER wire at the other end of the 3 wire black connector is NOT grounded. Then when you go to low speed...BOTH outer terminals should be grounded....then when you go to HIGH speed wipers the one terminal that had NO GROUND on it when it was in PARK is now grounded...and the wire that was grounded when in PARK is not grounded.

I can not understand WHY they do not want the motor to be bench tested. It is not like the electrical current from bench test is any different than the electrical current in the car if using a 12 volt DC power source and fuse. That makes no sense other than they must figure people will not do it correctly and cross wires and fry it out. I do it all the time with no problems due to I pay attention to what I am doing.

DUB

 

Hi DUB,

When I talked on the phone with the technical guy at Lectric Limited, he said that the motor needs to have a load on it when it comes out of park position and when it goes into park position. If it does not, then it messes up the indexing and will not function after that. He said all new motors come with the warning to not bench test the motor but instead mount it to the wipers and test it there.

Richard

 

Hi DUB,

(Failed) Have the wiper switch plugged in and test the outer two wires to make sure that you can get a ground on one outer terminal ONLY when the switch is in PARK.. So that means the OTHER wire at the other end of the 3 wire black connector is NOT grounded. (Both were grounded)

(Passed) Then when you go to low speed...BOTH outer terminals should be grounded....

(Passed ? Park failed) then when you go to HIGH speed wipers the one terminal that had NO GROUND on it when it was in PARK is now grounded...and the wire that was grounded when in PARK is not grounded (One terminal was grounded, one was not)

So DUB, I'm assuming that if the grounding is not correct in Park position, then the motor can not work even if the grounding appears correct at Low & High speed ?

Richard

Also, here is the new label, the wiper motor vendor is placing on all new motors:

 

You might use this to test the switch.

Here is how the switch functions and in most cases you can take the switch apart and clean it vs buying a new one... it's easy to do.

Also.. I find it odd that they say not to test the motor, because if tested properly it'll park itself.... personally, we bench test each and every motor we install before installation. Why install something that is not tested?

http://repairs.willcoxcorvette.com/w...tch-repair.pdf



Then there is even more info on the tech site about your system including how to bench test the motor at this link http://repairs.willcoxcorvette.com/?yt=&s=wiper+switch

1973-1982 Wiper Motor Testing.



Willcox

https://willcoxcorvette.com/
http://repairs.willcoxcorvette.com/