Symptoms
- Visible sparking through the motor housing vents
- Power gradually decreasing over months of use
- Intermittent operation or stalling under load
- Louder motor noise than when new
Likely causes
- CommonCarbon brushes worn down from normal useBrushes are a wear item by design and typically need replacement after hundreds of hours of use.
- PossibleBrushes not seating properly against the commutatorEven fresh brushes can spark if they're not seated correctly after replacement.
- PossibleDust and carbon debris built up inside the motor housingDebris from brush wear can accumulate and cause additional arcing.
- Less commonCommutator (the part the brushes contact) is worn or damagedLong-term wear can score the commutator itself, causing sparking even with new brushes.
What to do
- Unplug the drill before any inspection.
- Locate the brush caps, usually two small plastic or metal caps on opposite sides of the motor housing, and remove them.
- Check the length of the remaining carbon brush material; if it's very short or worn at an angle, it needs replacing.
- Replace both brushes as a pair, even if only one looks worn, using the manufacturer's matching part.
- Run the drill briefly without load after replacement to let new brushes seat, some sparking during this break-in is normal.
- If sparking continues heavily after new brushes are installed, the commutator itself may be damaged and need professional service.
Tools and parts
- Small screwdriver
Carbon brush replacement set for corded drillSearch: “drill carbon brush replacement set”
When to call a pro
If you're not comfortable opening the motor housing, a small appliance or tool repair shop can replace brushes quickly and inexpensively.
Safety
Use caution
Always unplug the drill before opening the brush caps or touching any internal components.