1999 Mustang Gt, Dashlight issue

Can someone please help me. I have recently purchased an all stock 1999 Mustang gt convertable. When i got it the dashlights would not work unless you cut the interior lights on, however only for a second and then the fuse would blow. I got a new dimmer switch and the mech. told me that it was fixed, however that only lasted for about five minutes when i cut the headlights on tonight and then the fuse blew again. I replaced the fuse only to find out that the dashlights would only work again with the interior lights on. Does anyone have any answers, Please.

get a wiring diagram and trace the circuit. from that you should be able to determine, through logical reasoning, where you have a short or unwanted ground. then you can figure otu where in the car it is and fix it. that's the best advice i think we can give.