DC Auto Windshield Wiper Motor Help!

[RogerB]

Guys & Gals,

I have a project to use a windshield wiper motor to drive a mini mill power feed. I converted a computer power supply for the juice and purchased speed direction control unit on eBay. I tested the electronics using a auto electric window motor and all worked as it should. I didn't have connections for the wiper motor at the time, but I did verify that at worked good.

So, now I have the project together, but the motor does not work as expected. It runs at a constant speed, doesn't slow down when I turn the speed controller down. When I turn the speed controller to stop and then reverse, the motor does not turn at all. I connected up the power window motor again and it works as it should; changes speed and direction of rotation.

I'm thinking the wiper motor is good, but has electronics that make it behave differently. So, my question is can I do something relatively simple to the electronics to get this motor to respond as needed? If so, what do I need to do?

If it can't be done with some fairly simple changes, I'll have to get another motor. I'm not doing this immediately because I have a lot of time invested in the motor coupling and mounting bracket for this motor.

Below are a few pictures of the circuitry in the motor housing.

Thanks in advance for any input.

Roger Barker

 

[ClydeCrashKop]

You could try bypassing all of their circuitry and wire directly to the brushes.
Hopefully on the circuit board.

 

[rjenkinsgb]

Is it a permanent magnet motor, or wound field?

The windscreen wiper motors I've seen have been "series wound" configuration, which is good for getting the maximum torque from the motor but not good for any kind of feedback-based speed controller.

Series Wound DC Motor or DC Series Motor | Electrical4U

A series wound DC motor like in the case of shunt wound DC motor or compound wound DC motor falls under the category of self-excited DC motors, and it gets its name from the fact that the field winding in this case is connected internally in series to the armature…

www.electrical4u.com

The smaller window motor was likely a permanent magnet type.

If your wiper motor does actually have a permanent magnet field, the tracing the brush connections and wiring straight to them like ClydeCrashKop says should work fine; but do not try that with a series wound motor, you are likely to destroy your speed controller.

 

[RogerB]

Ok, thanks guys,

I could feel very powerful magnets when pulling the housing off the armature. I see 3 brushes. So, should I run positive to all three?

Thanks again,

Roger

 

[ClydeCrashKop]

If there are 2 brushes directly opposite each other, use them. Positive and negative. Swap polarity for direction.

 

[saabnut]

Clyde is correct. the offset brush is for low speed.

 

[saabnut]

If one of the brushes has continuity to the aluminum housing that will be negative.

 

[shortbus=]

the offset brush is for low speed.

Are you sure about that? I was under the idea it was to reverse the direction at shut off, for a slight time, to park the wiper in the correct position.

 

[alec_t]

If you tried running the motor from the controller without back-emf protection the controller may now be toast .

 

[Externet]

And check its wiring path is not interrupted by a series and hiding 'park' position switch.

 

[Visitor]

The Post Apocalyptic Inventor on YouTube has a number of videos showing how to use wiper motors. Search his channel for some proven advice.

 

[rjenkinsgb]

Looking at the picture below; the four connections across the top (plug pins?), left to right, most likely configuration:

First two = fast/slow speed, either one or the other most likely.
Third = motor common (switched in the vehicle).
Fourth = permanent common, to parking position switch.

The third and fourth would be connected in any but the park position, via a rotary wiper in the gearbox.

I'd try 12V power across first & third positions & see if that runs?

 

[saabnut]

shortbus=
i have never seen a wiper motor with a reverse polarity park action.

 

[saabnut]

rjenkinsgb across the top from left wiper high, then low, or vice versa, then park circuit ( has power with wiper switch off) then ground. In the alternative far right is positive, and the others are switched to ground. Then also there is likely some intermittant function we do not need to consider.

 

[rjenkinsgb]

cross the top from left wiper high, then low, or vice versa, then park circuit ( has power with wiper switch off) then ground. In the alternative far right is positive, and the others are switched to ground.

Not possible.

The three pins that link to the motor stick up at the left; connecting to 1 - 3 across the top.

The third and fourth at the top are the park switch, so cannot ever have direct power & ground across them, as they are shorted for part of each rotation.

 

[RogerB]

Guys,

Thank you big time! Wiring positive to one brush and negative to the brush across from the first has the motor now working as it should. Speed is variable and direction of rotation changes with the controller. It does seem to run a little slower, but that's OK for this application.

Thanks again,

Roger

 

[shortbus=]

shortbus=
i have never seen a wiper motor with a reverse polarity park action.

GM in the late 1980's to some time in the 90s. If the motor didn't stop/park correctly overshooting the position, it would move slightly reverse to park.