Tip & How-To about Drills

How to Hot-Wire Test a Cordless Drill Motor

The power switch may not be the problem if a cordless drill stops turning on. Sometimes a bad drill motor can prevent the tool from starting, even if the switch is good.
To determine the problem, the best method is to remove the switch and then hot-wire the drill motor to the drill's rechargeable battery to test it. If the motor checks out, then it's probably the switch.
The steps for testing a drill motor .
In addition to tools needed for dismantling the cordless drill, such as a drill/driver, two wires are needed to connect the motor wires to the drill battery.

Hot-Wire Test a Drill Motor


1. Remove the drill's battery and dismantle the drill.

2. Disconnect the wires leading from the switch to the drill motor. Sometimes this means completely removing the switch.


3. Now that the motor is isolated from the switch, connect one of the motor wires to one of the battery contacts using one of the two wires set aside for this test.


4. Connect the second wire to the other battery contact.

(Note: It does not matter which motor wire is connected to which battery contact. The orientation is not important because it is a DC motor and will only determine which direction the motor spins.)

5. Hold the motor firmly in one hand, and then complete the electrical circuit between the battery and the motor by connecting the second wire to the the second motor wire.

If the motor does not spin once the second connection is made, then the drill motor is most likely fried and needs to be replaced.

If the motor does spin after completing the electrical circuit, that's a good indication that the motor is a healthy one. If the motor tests out OK but the drill is still having trouble starting up, the problem is most likely caused by a faulty power switch, not the motor.




The power switch will have to be reconnected to the drill after the motor has been tested. It is important to reinstall the switch wires correctly after performing this test.
The example drill used in this article has a very simple wiring configuration in its power switch. Drawing a switch wiring diagram is especially useful for switches with complicated wiring configurations.

If you're testing your drill's motor, chances are that some kind of part replacement is on the horizon.

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1 Answer

It seems to lose total power then it comes back only to lose again, possible switch problem?


Could be the switch. Check the terminals on the switch to see if one or more is bent or broken where the battery connects. Or the switch could be bad internally. Another thing to check is the motor brushes. Sometimes they get hung up and stop making contact with the armature. I doubt they wore out the tool isn't that old. The switch part number is N019952 the numbers for each brush are 640555-00 and 640550-00. You can order parts online at dewaltservicenet.com or call 1-800-433-9258

Jan 03, 2013 | Dewalt DC825 Cordless Drill

1 Answer

my dewalt cordless drill stopped working in the middle of drilling a hole. is the trigger faulty/broken?


First before you open the tool ground yourself. The switch is probably static sensitive. Now open the tool and check for wires that may have come loose from the switch, or motor brush area. If no bad wires make sure the switch terminals are ok (not broken or bent and are tight enough to make contact with the batery terminals). Next check the brushes and make sure they move freely in the brush holders. You didn't state the model so it may not have brushes you can access. If all that is good disconnect the motor from the switch and secure the motor in a vise. Take wires with alligator clips and connect the battery directly to the motor for just a second to see if it runs. If the motor runs you have a bad switch assuming your battery is charged.

Dec 08, 2011 | Dewalt 18 Volt Compact Drill Kit

1 Answer

my 15.6v cordless has just stopped working. could it be the switch ? recently it had been making a slight noise when being used. thanks.


did it also have a burning smell?? what you can try first is "tapping the drill on the end" if it starts again the motor is bad. I probably replace more motors on these than I do switches and if you said it was making a noise I would have to think it is gone. Let me know.

Aug 13, 2010 | Panasonic 15.6v Ni-mh Cordless Drill -...

2 Answers

Finger Switch


Call1-800-423-3598,give them your model number so they can send a replacment trigger assy.

Dec 08, 2007 | kawasaki 19.2V 4 Piece Cordless Tool Kit

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