PLEASE HELP - DC motor testing

Thread Starter


Joined Oct 19, 2017
I have a brand new (reman) wiper motor from a 69 GTO. The wiper actuator was broken, but I want to test the motor. I have removed all the casing minus the motor (stator, commutator, etc). The motor is a brush motor with a Poss and Neg lead that I try testing using a 9V battery. However, I know nothing about testing these motors. When I hook up the 9V battery, the magnets in the stator activate, and the commutator assembly does not spin...but is magnetized to the stator (or vs versa). Even if I turn the Commutator to get the polarity opposite, it does not begin to spin. Does this mean that the windings/wiring in either the rotor assembly or the stator are backwards?


Joined Mar 14, 2008
Does this mean that the windings/wiring in either the rotor assembly or the stator are backwards?
It likely means your 9V battery is woefully inadequate to deliver the current the motor needs.
If you don't have a power supply, I suggest you connect to your vehicle's battery, or make up a battery of nine 1.5V alkaline D cells in series.


Joined Sep 9, 2010
It likely means you used a tiny 9V battery that has nowhere near enough capacity to activate the motor. Measure the voltage at the battery poles when you make the connection. But save the bother if I'm right about using a "transistor" battery.


Joined Jul 18, 2013
If it is pre 70's then it most likely is a wound field motor, you don't turn the rotor to reverse dir, it is either done by reversing the armature or the field, if wound.
Both have to be energized, there also could be a park switch in the motor mechanism.
Wiper motors take a lot of current as already mentioned.
Cannot you try it on the automotive battery in you car?


Joined Nov 18, 2012
The motor needs to be connected to an automotive 12v battery. It could take 10-15 amps of current to get it started and then it will settle in around 8-12 running amps. Your little 9v battery does not have the capacity to start or run this unit. The armature, brushes and field (case) should all be properly assembled for it to run correctly.