DIAGNOSIS A capacitor on the main circuit board is discharging. This is normal for a very short time after removing the battery. If it stays lit for more than 30 seconds, it indicates the capacitor is holding a charge longer than it should.
FIX This is usually harmless and doesn't affect performance. To fully drain the capacitor and turn the light off, pull the trigger (with no battery installed) until the light goes out completely. This discharges the stored energy.
IF THAT DIDN'T WORK If the light remains faintly lit for minutes or hours, there's a minor fault in the LED circuit. It's a parasitic drain, but with the battery out, it's not a problem.
HEADS UP This is not a sign the tool is "on" or draining your battery when stored. The main power circuit is definitely off. It's just a quirk of the LED's design in some units.