Electric Drill: No Variable Speed

Worn carbon brushes can impact the flow of electricity to the armature, as well as a heavy dirt build up on the carbon brushes. To inspect the brush as the probably cause, open the drill case and locate the brushes. Lift up the brush holders by pulling gently on the wires. Inspect the brushes for wear and damage. Brushes close to 1/8 of an inch, or less, need to be replaced. If the brushes are good, but dirty, them they should be cleaned. Push down on the tab on the side of the brush holder to remove the brush and spring. Clean out the inside with electrical contact cleaner. Clean the spring and brushes as well, if using old brushes. Install the brushes back in the holder and lock the tab in place. Reinstall back on to the drill, using a small screwdriver to hold the brush down as you insert it. Tuck the wires in their appropriate channels, so they do not interfere with the case when you close it. Finally, reassemble the case.

The variable speed switch controls the speed of the motor by adjusting the flow of current. The variable speed is a normal part of the main trigger switch. To replace the variable speed switch, open the two halves of the drill case. Remove any hold down screws on the switch. Disconnect the electrical connectors then take the hold switch out of the case and install a new switch. Attach the electrical connectors to the appropriate connections and reinstall any hold down screws. Finally, reassemble the case.