Recommend sanding the contacts on the battery clean if you have issues like dim lights, it's also one of these contact pads that is the switch to turn the red LED on when you insert the battery pack, the spring contact inside the gun needs to exert pressure on it. Or if your LED is on all the time as mine was, I needed to excercise that switch manually a while and used compressed air on it. It doesn't move much if at all but it's the switch.