• Hello there guest and Welcome to The #1 Classic Mustang forum!
    To gain full access you must Register. Registration is free and it takes only a few moments to complete.
    Already a member? Login here then!

1970 Mach 1 wiper motor theory and operation

M

miketyler

Member
I took my wiper motor apart to clean and relube it and now it doesn't park. Not sure if it did before or not since it was in abox with the car when I got it. So I could take the easy way out and just go buy one from OReilly's but that just isnt me. To go buy another one admits defeat.

The book doesnt explain the theory, only testing and replacement. The unit motors thru ok. Blue and white are the high and low speed wires ad I presume it does this thru resistance wires. What I dont understand is what is happening electrically when it is in park cycle. Apparently the white wire is grounded while power is still applied to the motor over the blue or white wire? I've taken it apart a few times now and dont see how this should operate. Please someone dumb it down for me.

Here is the park bench test (no pun intended) diagram. Will post some pics of the brush and switch plate.
 
They are very simple, actually. You should see a set of contact points inside the motor, much like the mechanical voltage regulator, or actual distributor points.

Now the motor actually has 2 power wires going to it. One supplies power to the motor all the time that the key is in accessories or run. The other only has power when the wiper switch is on. With the wiper switch on, it allows power to by-pass the points and even though the points are opening and closing (there's a little cam in there that opens and closes them as the motor turns), the opening points have no effect, because of the by-passed wire.

Then when you turn the switch off, the motor keeps turning until the points open, killing power to the motor and the wipers turn off. It's all set up so that when the points open, the wipers are in the "parked" position. This is how they continue to run until the parked position, then stop.

You're problem is probably with the points or a wiring problem. If the points aren't opening, they can never park, or even turn off, for that matter, without the use of a separate switch to kill the power to the "constant power".

I had this exact same problem with my son's '65, and was able to shim the cam on the points, to get it working correctly, and never had another problem with his wipers the rest of the time we owned the car.
 
Thanks for the response, the points are opening and closing correctly and I am getting continuity from the plug to each of the wires going into the motor. However, jumpering the ground and the white wire and applying power as shown in the illustration and applying power to the red does nothing. I would have expected it to run shortly until the points open. Not a dead short but seems the power wire gets hot like there is a short during the test.
 
Ground the motor to the chassis and retest. There is a note to be sure the motor is grounded during the test.

Is that supposed to be a functionality test? It says current draw test......
 
So my question is has anyone fixed on that wouldnt park? The manual talks about replacing "the park switch". I am unsure what that is? Any wiper motor technicians here?
 
The only knowledge I know about wiping is what my parents taught me when I was very very young.
 
Dont know if the 70 is the same as the 67, but my 67 wiper parking issue was caused by the washer pedal switch. Apparently, the parking circuit on the 67 includes the floor mounted washer pedal's switch, and a fault in it prevented the signal to park the arms.
 
I think the 70 is different as there is no pedal washer; is dash mounted switch if I recall. That is interesting nonetheless.

What I have noted is that inside the motor there are three brushes instead of two. I may be wrong but I believe the motion on the park circuit is controlled thru this pulsing switch and delivered thru the third brush.

Regular operation is managed thru either of the speed wires but when power is tunred off, the two brushes are de-energized. At that time the third brush becomes energized and the motor continues to spin thru 180* of rotation at which point the leaf contacts close (or open) and the motor stops.

During the park test, my motor spins continuously thru the park cycle but there is a noted "hiccup" with each rotation probably where the plunger hits the leaf contacts. I can only guess the main speed brushes are staying energized when they should be cutting out?
 
You must log in or register to reply here.
Back
Top