66 Windshield wiper motor Help Please

[Scott P.]

A friends 66 WSW motor case with key on only will light up a test light.
Thats in the car or being bench tested.
Using a drill motor 12volt battery and jumper wires to bench test the WSW motor
with the motor running, it will light up a test light when touching the motor case and grounding the wiper case as normal.

How is this possible.

The complete unit was disassembled. No bad wires found, coil works fine, the board isnt a problem. This cant be normal.


On top of that, I have a NOS WSW motor assy still in the GM box. I opened the box, took out the WSW unit and bench tested it
the same as above. It to will light a light.

Scott

[Richard M.]

Re: 66 Windshield wiper motor Help Please

Scott,

Does his motor run normally, or inop?

What exactly are your test light connection points? Tip to case, other end lead to where?

Is the separate copper ground strap connected to the case?
You may be simply lighting the lamp from the case if its a floating potential, i.e. the case is not properly grounded.

Is the test light simply a bulb with 2 leads, or is it a battery powered test light?

The case is ground, and the brushes connect the field coil windings and via the commutator contacts to the armature from power to ground through its windings, both coils are very low ohms. I don't recall how these motors are wound, series or shunt wound.

Series wound means power is sent to the field coil first, then to armature, then to ground.

series-dc-motor.png

Shunt wound means the field coil and armature get power in parallel , then to ground.

shunt-wound-dc-motor.png

Then there's compound, a combination of both.

compound-dc-motor.png

[Scott P.]

Re: 66 Windshield wiper motor Help Please

Richard,
The WSW motor runs just fine in either low or high speed.
The test light has alligator clip on ground which is clipped to the ground strap which is bolted to the case as normal.
The light bulb will light any place you touch on the unit thats metal.
This is a bench test. A 12volt drill motor battery with positive to the center spade for testing per the manual.
The battery negative is touched to the WSW unit. When touched the motor will operate.
The test light is simply a bulb with 2 leads. Sort of.
I have a battery powered test light that when I touch the WSW with my hand then touch the WSW with the battery powered prob, it will light up and buzz.
I dont understand your last to statements.
Thanks Scott

[Richard M.]

Re: 66 Windshield wiper motor Help Please

Scott I was just talking motor theory, thinking your test light was a powered type, therefore resulting in continuity through the low ohm field or armature windings, typically only a few ohms. But since I now see your test leads were basically touching 2 areas of a grounded chunk of metal, it's clearer to me now.

However, connecting a simple bulb type test light between two areas of the grounds of the motor case would never light up. A simple bulb type test light is not a continuity tester. It is a means to verify voltage points with respect to ground.

I suspect your first test light, (you said "sort of"....which is a bit confusing) is actually powered, so you're simply showing continuity between 2 connected areas of the case metal.

Your second "powered" test light must be a sensitive type which is using your body as a conductor. Totally predictable.

You are triggering your test instruments and seeing normal results of their use. The metal case and ground strap is tied together by design. If you were to use a high quality ohmmeter you would see the same continuity result, yielding around 0.2 ohms, with likely around 0.1 ohms error in the meter leads, to be subtracted from the total reading.

Since both motors function, it appears you're just seeing some unusual test result artifacts from your test methods.

Rich

[Scott P.]

Re: 66 Windshield wiper motor Help Please

Rich, thanks for your insights.
This whole deal started when we were working on the 66 engine, getting it to run. While doing this one of the BB wire mesh covered spark plug wires touched the WSW motor case and it sparked. Later I came back and did the BB wire mesh plug wire covering to the WSW motor case test and it still sparked.
We removed the WSW motor for a bench test and to be able to disassemble it if necessary to find the problem.
Hence the first post.
Scott

[Richard M.]

Re: 66 Windshield wiper motor Help Please

Ok, I see. But I believe I know why....

The WW Motor ground is a separate black wire which starts at the starter attachment bolt, up to the blower motor, then into the engine harness and ends at the wiper motor as a individual plug.

The WW Motor is always powered in RUN or ACC, and uses ground to turn on, high or low speed via the dash switch.

If the source ground is missing or intermittently conductive, then attaching engine ground, i.e. the plug wire sheathing now creates its ground path. The missing ground would typically cause a clicking sound in the motor mechanism.

However, another oddity can occur if that source ground black wire is inadvertently attached to the Bat+ stud on the starter solenoid in error. The terminal is 3/8" ID, and easy for one to assume it goes there. It belongs on ground via the starter bolt.

If on Bat+ the motor case is now at a B+ potential. Touching the motor case with a grounded sheathing of the plug wires would certainly cause your sparks to occur.

Check his black ground wire for proper connection.

Rich

[Scott P.]

Re: 66 Windshield wiper motor Help Please

Richard, I did check that ground at the time but I will do it again. The wipers did operate at the time and if the grd wasnt there they would not have.
The AC blower motor is on the same ground path and it functioned.

Back to the bench test. 12volt drill motor battery, pos to center terminal, neg loose to touch case to make run.

Scott

[Richard M.]

Re: 66 Windshield wiper motor Help Please

Richard, I did check that ground at the time but I will do it again. The wipers did operate at the time and if the grd wasnt there they would not have.
The AC blower motor is on the same ground path and it functioned.

Back to the bench test. 12volt drill motor battery, pos to center terminal, neg loose to touch case to make run.

Scott

Scott,

Wilcox had a good bench test guideline. A copy can be found in the Document Database Sticky thread Main page under "Wiper".

Here

There are some test details which may help. It includes some fault diagnosis info regarding the dash switch too. If something is miswired there it may be relavent.

Rich