Is it the bulb or the connector? I had a prob where every 50 miles or so the tail light would go out. I had to take the tail light assembly out and take the connector apart and lighty re-crimp the connectors where they slide together from the vehicle harnass to the lens assembly. They had loosened up trom vibration. Also check for corrosion around the opening where the bulb fits into the assembly as it is the connection point. Check the connector