Wiper motor test

[Danman09]

I removed the wiper motor from the 1970 C10 project I bought while I am replacing the dash harness.
I looked here and found the bench test steps and tried it. When I ground the case, put power to the power lug, the motor runs without providing a ground to either the high or low lug.
So I take it that the motor is bad even though it runs ?
Just wanted more opinions than mine before buying one that is probably an inferior product to the original.

[BigBird05]

I don't believe you are testing it correctly. the three terminals on the wiper are used for testing the yellow wire is hot ( power all of the time because the switch controls the ground ), the LT blue is one speed ( I can't remember if it is high or low ), and the black is ground.

[Danman09]

I was going by the steps LockDoc had posted Ray's Chevy site. His first step was to ground the housing which make sense because the housing would be grounded when installed.
However, if I do Not ground the housing the low and high speed works according to the test.
Just a little confused why grounding the housing would make it run all the time, since it will be grounded when properly mounted. Or am I wrong about that ?

[BigBird05]

Check back with lock Doc, but the housing is mounted on 3 rubber mounts and the manual doesn't show it as grounded.

[LockDoc]

Originally Posted by Danman09

I removed the wiper motor from the 1970 C10 project I bought while I am replacing the dash harness.
I looked here and found the bench test steps and tried it. When I ground the case, put power to the power lug, the motor runs without providing a ground to either the high or low lug.
So I take it that the motor is bad even though it runs ?
Just wanted more opinions than mine before buying one that is probably an inferior product to the original.

Can you post pictures of the connector terminals on the motor and how you are hooking it up? It depends on if it has three or four terminals on the motor.

LockDoc

[LockDoc]

Originally Posted by BigBird05

Check back with lock Doc, but the housing is mounted on 3 rubber mounts and the manual doesn't show it as grounded.

One of the rubber mounting pads has a built in ground strap. It is riveted to the motor bracket. It can be hard to see. The arrow is pointing to it.

LockDoc

[Danman09]

Sorry, but I seem to be too dumb to post it.
However, it is a 3 terminal motor, rectangular. Laid down with the terminals facing up, the one on the far right is the hot one, which is right next to the high speed ground. then a space before the low speed ground on the left.
If I do not ground the housing at all, but connect the 12 V to the right terminal, then ground the middle one it runs high speed.
Then , leaving those wires in place, I connect another ground to the left terminal it goes to low speed.
All seems ok.
As long as I do not ground the housing. But that is a problem because a wire to grd from housing with only a 12v lead to the hot terminal on left starts the motor.
I am assuming there is a short between one of the ground lugs and the case ?

[Danman09]

I posted the picture of the motor....somehow....

[LockDoc]

Originally Posted by Danman09

Sorry, but I seem to be too dumb to post it.
However, it is a 3 terminal motor, rectangular. Laid down with the terminals facing up, the one on the far right is the hot one, which is right next to the high speed ground. then a space before the low speed ground on the left.
If I do not ground the housing at all, but connect the 12 V to the right terminal, then ground the middle one it runs high speed.
Then , leaving those wires in place, I connect another ground to the left terminal it goes to low speed.
All seems ok.
As long as I do not ground the housing. But that is a problem because a wire to grd from housing with only a 12v lead to the hot terminal on left starts the motor.
I am assuming there is a short between one of the ground lugs and the case ?

If what you said above that I highlighted in Red is true then....

Your problem is that the terminal on the left by itself in your picture is not a hot terminal. The terminal on the right in your picture is the 12v hot terminal. Looking at the picture below the Yellow wire is the hot wire. Black and Light Blue are both grounds from the wiper/washer switch. The Brown connector is the washer connector.

[Danman09]

Sorry, I meant the terminal on the right, the one on the left is the low speed ground terminal.
If I ground the housing and touch 12v to the RIGHT terminal the motor runs with ground on either of the two ground terminals.
If I remove the housing ground and just ground the high or high and low speed with power on the right it also runs. That part is normal. That is why I am confused. But it doesn't take much to confuse me.

[LockDoc]

Originally Posted by Danman09

Sorry, I meant the terminal on the right, the one on the left is the low speed ground terminal.
If I ground the housing and touch 12v to the RIGHT terminal the motor runs with ground on either of the two ground terminals.
If I remove the housing ground and just ground the high or high and low speed with power on the right it also runs. That part is normal. That is why I am confused. But it doesn't take much to confuse me.

If the motor runs with a ground wire to the case and power to the terminal on the right side then it must have an internal short like you suspect. I am headed out to the shop in a minute here and I will try that test on one of my motors just to double check it.

LockDoc

[LockDoc]

Originally Posted by LockDoc

If the motor runs with a ground wire to the case and power to the terminal on the right side then it must have an internal short like you suspect. I am headed out to the shop in a minute here and I will try that test on one of my motors just to double check it.

LockDoc

Tested one of my motors with power to the right side terminal and case grounded and it does not run.

LockDoc

[Danman09]

Thank you so much. As I look through all these posts it is so often that you are the one who steps up and goes the extra mile to help out guys like myself who are knowledgeable about these trucks.
Thanks for going the extra mile for us all.
I will take the motor apart and have a look around in there to see if I can spot anything wrong.

[PepperTreeGarage]

Ths may help............. https://www.youtube.com/watch?v=HYLnGaZe6zY

[Danman09]

That is the video I watched b4 testing the motor. Now I just have to take it apart to try and see where the problem is. That should be interesting.

[LockDoc]

Originally Posted by Danman09

That is the video I watched b4 testing the motor. Now I just have to take it apart to try and see where the problem is. That should be interesting.

Thanks for the Kudo's. That's what's nice about having all of those parts laying around....

I would start by cleaning the paint off of the terminal contacts and give them a close look.

LockDoc