Trigger doesn't control speed, drill only runs full speed

Symptoms

• Light trigger pull gives full speed instead of a slow start
• No difference in speed no matter how far the trigger is pulled
• Sudden jump to full speed partway through the pull
• Problem is consistent, not occasional

Likely causes

• CommonInternal variable-speed control module has failedThis electronic component inside the trigger reads pull distance and fails as an all-or-nothing switch when it breaks.
• PossibleTrigger mechanism gunked up with debris affecting the pull sensorDust inside the trigger housing can interfere with the sensing mechanism.
• Less commonBattery voltage too low to modulate properly on some modelsA very weak battery can behave oddly with variable-speed electronics.
• PossibleThis is actually a single-speed tool, not a variable-speed modelSome basic drills and most impact drivers only have on/off or limited speed control by design.

What to do

1. Confirm from the manual or trigger design whether the tool is actually meant to be variable-speed.
2. Test with a freshly charged battery to rule out low voltage as the cause.
3. Try light, careful trigger pulls at different distances to see if there's any variation at all.
4. Clean around the trigger area with compressed air in case debris is interfering with the sensor.
5. Note whether the issue is constant or intermittent, since intermittent problems can still point to a failing but not fully-dead module.
6. If speed control never varies with a good battery, the trigger's internal speed control has failed and needs replacement.

Tools and parts

• Compressed air

When to call a pro

This almost always requires trigger switch replacement, which a small tool repair shop can usually do quickly.

Safety