Multi-Tool: Variable Speed Doesn't Work

The switch controls the flow of electricity to the motor and, on some models, and also controls the motor speed. The switch can wear out over time and become inoperable. To check the switch, remove the collet nut and front cap. Remove the brush caps and brushes. Separate the two halves of the housing and remove the power cable connector and screws that secure the motor assembly in place. Lift the motor assembly out and then separate the field from the switch by pulling them apart. Remove the wires by inserting a small pick next to the wire and then pull out the wire and pick together. Inspect the switch for burn marks, or melting, indicating a bad switch. Install a new switch, if you notice any of these conditions.

You can check the switch for continuity with an ohmmeter. Attach the leads from the ohmmeter to the wire connectors located on the switch. If the switch is good, the ohmmeter will give you a reading in the ON position, but will not give you a reading in the OFF position. The reading should change as you adjust the variable speeds on the switch. If you do not get a reading in the ON position and/or the value does not change when you adjust the speed, then the switch requires replacement.

Install the wires into the switch by simply pushing them in. Connect the switch to the motor and place everything back inside the housing, securing it in place. Reassemble the housing back together and reinstall the front cap, collet nut, brushes and caps.

Some models have a circuit board that controls the speed of the motor. If you can no longer adjust your speed, you will need to replace the circuit board. Remove the collet nut and front cap. Remove the brush caps and brushes. Separate the two halves of the housing and remove the power cable connector and screws that secure the motor assembly in place. Lift the motor assembly out. Examine the board for burn marks and damage that would impact its performance. Always replace circuit boards with burn marks as this is an indicator that they no longer work. It is a good idea to take a photo or make note of where the wires attach too. Disconnect all wires on the cold circuit board and attach them to the new one, referencing your photo or notes. Install everything back in the housing and reassemble the housing. Install the front cap and collet nut. Finally, install the brushes and brush caps.

Some models will have a controller. If the controller fails, you will not be able to adjust the speed of the motor and the on/off function of the motor may not work. To replace the controller, begin by removing the brush caps and brushes. Remove the front cap and the collet nut. Open the two halves of the housing by removing the screws that secures it together. Locate the controller in the handle and make reference of where the wires connect too. Lift the power cord from the housing. Disconnect the wires from the old controller and connect them into the new controller. Reassemble the controller back in the housing and secure the power cable down in the housing. Rejoin the two halves of the housing and then reinstall the brushes and brush caps, followed by the front cap with the collet nut.