I recently just bought a 1994 mustang gt 5 speed with 92,000 miles its has the mach 460 radio installed. The radio turned on but there is no sound at all. Until today. I went to get in my car turned on the key with my door open and there was sound out of the back speakers but not the front. That is until i shut the door then poof no more sound. I've checked all fueses and I've checked that the amps at the rear have power with a test light.