Defective Bulb shunts cause most light set failures. Simply plug your LightKeeper Pro into the light set and pull the trigger. The LightKeeper Pro sends a pulse through the light set, finds the bad bulb, and fixes the shunt allowing the light set to work properly.Convenient organizer for bulbs and fuses built into the handleQuickfix trigger- repairs the most common problem of the lightAudible voltage detector- helps locate circuit interruptions caused by loose bulbs, twisted wires and other problemsBulb pullerBulb and fuse tester