Take a test light and stick it in the middle of the bottom of the socket. You should have power there. If you dont, pull the socket and see if there is power going to the socket in the back. If you have power, then replace the 12 V socket. If you don't you may want to recheck your fuse box to see if there are seperate fuses for the front and rear 12 V's. If none of that works then you will need to get a wireing diagram and just follow your power wire untill you find where you lose power. But more often then not it is either a fuse or a socket. Good luck.