Renault Megane 1.6 cigarette lighter problem?

Hi,

The cigarette lighter by itself works fine, but when I try to plug sat nav into the socket there isn't any connection found. Normally once the sat nav is plugged in it lights up and works but there are no lights to suggest any power is getting to it.. I have tried the sat nav in another car and it works fine.. is there anything I can do..

Any help would be greatly appreciated :)

Thanks