You could always tap into the fuse box and be sure you are on the south end of the flow or you could go into another power line like the radio, if you choose to go to the batter directly be sure you use a 5amp in line fuse, I would first pull the factory lighter out and check connectons and RR

__________________
Jerry

2004 SL500 Black 55K Miles
2002 s500 Black 90K Miles
1986 300E Gold 233K Miles
1966 Twin Cessna 320D
1989 Jeep Cherokee 233K Miles
1994 Ford Van E150 399K Miles