12DC gear motor burning out in car.

Thread Starter


Joined Apr 23, 2009

I have a 12v DV motor like this one in my car that has burnt out (stopped working) several times. I replace the motor and it works for a while then stops.

The motor is connected via a fused line to the battery.

I measured with my multimeter and found that there is 12v to the motor when the car is off and 14v when the car is running.

This is a reversible motor hooked to a DPDT switch.

I did notice that there is constant power to the motor even when the switch is not pressed but there is no ground to the motor unless the switch is pressed.

My questions are:

1. Do I need to limit the voltage to 12v?

2. Would the constant voltage burn out the motor?

Any help is appreciated.



Joined Apr 5, 2008

You should limit the voltage to 12 Volts.
On the page it says "Operating Range: 3-12VDC".



Joined Feb 4, 2008
Use a low drop out voltage regulator to regulate the voltage to 12V.

What is the motor used for?

Thread Starter


Joined Apr 23, 2009
The motor opens and closes a flap for an exhaust cutout.

Is there any source in the car that is already limited to 12v?

I tested a cigarette lighter socket and it was at 14v when the car was running.

Thread Starter


Joined Apr 23, 2009
The company that I bought the cutout from may replace the motor.

I've only seen 12v or 24v models.

Is there a power source in cars the is already regulated to 12v?
As someone stated above, the 12v model can operate down to 3v. What is the operating range of the 24v model? Check the operating specifications, power and others, to see if it would work in your application.

There might be 12v regulated power on the car but I would imagine it would be a great deal easier to take the suggestion that has already been given, adding a low drop out voltage regulator. Not only would a regulated 12v point need to exist but there would need to be enough extra power in the deisgn to drive an additional motor. Don't count on that.

Thread Starter


Joined Apr 23, 2009

I'll get the regulator, is this the correct one?

Also, I see there are three pins, how would I wire the regulator?

Thanks to all for the help.


Joined Jul 17, 2007
Looks like a surplus motor that's being sold as a wide voltage supply range for maximum profit.

I'd be willing to bet that the seller does not have the manufacturer's specifications for the motor, but will be quite happy to continue selling them to you as they burn up.

If you want to make them last awhile, I suggest that your solution would be to use PWM at around 50% duty cycle (averaging 7v) rather than trying to use a linear voltage regulator. PWM (Pulse Width Modulation) is an effective and highly efficient method of controlling current through a DC motor.

You can build a PWM circuit using a 555 timer, a power MOSFET, a capacitor and a few resistors. It's a bit more complex than using a linear voltage regulator, but will work much better and be far more efficient.

I'll have to guess that you're pretty new to electronics. Have you ever built an electronics kit before?

I'm just trying to get an idea of how far along you are. Many here are brand-new to electronics, many are old-timers learning new things, and many have advanced skills. Our challenge is to adapt to your level of experience. We'd like to assist you in completing your project, but without an idea of where you are....