36v GE motor...commutator bars ALL showing .6 ohms to each other?

[jeremy360]

Does this mean that they are all shorted out? Seems odd that everyone would be shorted. I was under the impression that the commutator bars 180 degrees from each other should ohm out together, the rest not. Am I wrong?

The one thing I did do was lightly use some sandpaper from a roll to shine up the commutator surfaces while I had everything apart changing the input shaft collar. I read where emory cloth is not to be used because of the conductivity, and I assume my sandpaper was aluminum oxide, so it could be conductive too, but I took a stiff bristled brush to make sure there was no grit left behind.

I put everything back together and the cart (1994 marathon) wont go again. I tried taking off all wires and putting 12v directly to the motor per the images posted here. Motor did not spin, only got sparks when connecting.

A1/A2 terminals ohmed .4 ohms. S1/S2 terminals ohmed to .3 ohms. No combo of A/S had connection to each other, nor to ground. Which is what baffled me to get sparks when I hooked up.

Has anyone ever ran into anything like this before?

[mjroman20]

I've been curious about this myself. A colleague and I have performed this test on several motors, some suspected bad and others brand new and functional. But the results are consistent with what you are observing.

I know little about actual motor design but my thought is they are configured almost like a large circular potentiometer. I can tell you this much, the brushes are configured at 180deg - that is the A1 post is connected to a brush at 12 and 6 o'clock while A2 post is at 3 and 9. So regardless of the position of the armature you should have the same values between A1 & A2.

[Raystar57]

I am not a motor expert but what you are seeing is the norm.
Armature winding can be quite complex depending on the motor.
The use of specialized testing gear called a growler can identify a real short in the armature.
https://en.wikipedia.org/wiki/Growle...ctrical_device)

In the very simplified pic below you see that the wiring causes all commutator bars to be electrically shorted.

Search on armature winding and check it out.
I got dizzy looking at all the wiring maps...

[jeremy360]

OK....any other reason you'd see that would cause a motor not to work with voltage directly applied? The brushed look good and wires to them good. A1/2 ohmed good....same for s1/2....and none to ground. I have to be missing something. Thanks for the responses by the way.

[Raystar57]

Ok, insure the motor is installed on cart and cart on jack stands before testing.

Are you testing it as a series motor?
It seems you have a series motor (S1/S2).
There will be some sparking as you make the final connection but motor should spin in a short time. At least within one second.

Insure the brushes are not binding in the guides.

Originally Posted by 93yellowclubcar

Here's the info on how to bench test an electric motor, this is originally from Stevegrmich.


To test run a SERIES motor

Remove all cables from the motor; connect a jumper from A1 to S1. Connect 12 to 24 volts, positive @ A2 and negative @ S2. Swap S1 and S2 to change rotation direction.


To test run a Sep-Ex (regen) motor

Remove all cables from the motor; connect a jumper from A1 to F1 and a jumper from A2 to F2. Connect 12 to 24 volts, positive @ A1/F1 and negative @ A2/F2. Swap F1 and F2 to change rotation direction.

CAUTION:
Allowing a motor to spin @ high RPM can cause catastrophic failure!

[jeremy360]

Series. Brushes not sticking. I didn't leave connected when it sparked. Will have to try leaving for a second or two.

[Raystar57]

Originally Posted by Raystar57

The use of specialized testing gear called a growler can identify a real short in the armature.
https://en.wikipedia.org/wiki/Growle...trical_device))

Updated link.