Hit the brakes and the radio went off and the map light went on... go figure.
Brake light circuit (7) had blown fuse.
Changed the fuse and now no radio and no Brake Lights.
Anyone out there have any ideas???
Hi Javier. That's no fun.
*According to my 1973 wiring diagram, the Chrysler map light and brake light are on the same fuse. The radio is on a different fuse. If 1978 is same, then:
*If the brake light/map light fuse blew, the map light had to be getting power from somewhere in order to come on.
*My guess is a short between the map light and radio wiring. You hit the brakes, wires shift position slightly, short occurs, maps light takes radio power. Map light comes on, radio goes off. Another shift of position due to braking, accelerating, cornering, or wiggling of wires and intermittent short goes away.
*20 amp fuse will last until wires shift again and short reappears
*I'd be looking for continuity between the wire connector at the back of the radio and the wire connector for the brake light switch. Once I had my ohmmeter hooked up, I'd wiggle wires and see if continuity appeared. It helps to have an assistant watch the ohmmeter while you're wiggling wires.
*Not sure if your car has rear speakers, but if it does, I'd look for a place of wear, like the edge of a sill plate, and look for a short below. Also, any place where there might be water damage is a likely spot. Best of luck!