I have a 12v electric motor (windshield wiper motor) that I am trying to slow the rpms on. This is not still in a vehicle. I've mounted it to a coffin and am using it to pull the lid closed as it makes a revolution therefore making a coffin that opens & closes itself.
Thought of trying a pot but not sure of size to use and I don't know if it would slow it down without minimizing any of the motors power. Any suggestions will be greatly appreciated.:confused:

Yep, This PWM kit will work wonders.
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You have to put it together.

Kiss, great site. Where you attach from pivot point can change speed of opening and closing, or is motor at pivot point? Counterweights may help to relieve some stress from Motor.

Strat:

I'm giving away all my secrets. <G>. I've used that PWM modulator for an off-the-wall application, a solenoid driver. Because of it's slow start capability, I used it for a shutter driver where the shutter located near a $1000, <1mm thick lens. I wanted to cut down the vibration. This was about the time solenoid driver IC's were developed. My other solenoid drivers dissipated too much heat. They really need kick, move and cut-back values.

Kick because of static friction, Move because of friction while moving and cut back to run at minimum power when energized.
I did play with it on a car heater motor, but the motor sung too much. I didn't play with the frequency much. Now I have automatic climate control, so I don't need it there.

Will this reduce motor speer without reducing power? Tried using a 9v power supply - slowed to about the right speed but not enough strength to move the door.

Yes. It will control speed without reducing power.

Here is all the info you should need: Velleman Components n.v. (http://www.velleman.be/ot/en/product/view/?id=9391)

You will need a power supply with it. 12V will be fine.

With the kit a variable duty cycle square wave is applied to the motor, thus torque is still at the 12V level.

How to slow down the power window motor?anyone can help me?

Do a web search for "12 volt dc motor speed control" and you will find many products that will do what your asking for.