DIAGNOSIS You have an intermittent electrical connection. The most likely culprit is a cracked solder joint on the trigger switch's circuit board or a loose wire connection inside the handle.
FIX Open the drill and inspect the trigger assembly connections.
- Remove battery and housing screws.
- Carefully open the clamshell halves.
- Check the wires from the battery terminals to the trigger, and from the trigger to the motor. Look for loose spade connectors.
- Reseat any loose connections. If you see a cracked solder joint on the trigger board, the whole trigger needs replacement.
IF THAT DIDN'T WORK If connections are solid, the trigger/switch unit itself is failing intermittently. The physical impact temporarily reconnects internal contacts. Replace the trigger switch assembly.
HEADS UP The "percussive maintenance" (whacking it) is a temporary fix that worsens the problem. Each impact can loosen other connections or crack plastic housing clips, leading to more failures.