Why did my car stereo catch on fire?

Question

I'm not sure what went wrong, we were hooking up my car stereo, so that the speakers worked and the settings stayed saved. We were almost done with it, it was put back in the dash all screwed in and everything, the speakers worked, the settings were saved and working, and the radio was off. We were just putting the last few peices together and the next thing we knew smoke was coming out of the dash, lots of smoke. We ran over to the battery to unhook the battery connecter (we had to run it straight to the battery). We had it hooked to the positive side. Smoke was pouring out from there too, and i could see the wires glowing orange. After prying the battery connector off the smoke went away and it cooled down. WTF happend here? The wire burned from just below the radio all the way to the battery.

Answer 1

Was the power wire stripped somewhere and touching bare metal? You shouldn't have had to hook it into the battery. there should be wires in the dash for it to connect to. Switching the power and ground or them accidentally touching is the only thing I can think of.

Answer 2

Any wire, no matter what size, is a fire risk if you connect it to the battery terminal without a fuse.  

All the metal structure of the car is connected to the negative battery terminal.  If you connect a wire to the positive terminal, then pinch it against a metal surface somewhere in the car, then  you have a short circuit.  High current instantly starts running through the wire, causing it to heat up and catch fire.  When you use a fuse, it blows when high current starts running through it, thus breaking the connection and protecting your wire.

When you put the radio back in the dash, somehow the wire from the battery came in contact with metal in the dash.  It might even have gotten pinched against the metal chassis of the radio itself.  (with your radio connected, the metal chassis of the radio itself effectively becomes part of the metal in the vehicle).

I'm afraid you've learned the hard way that any wire you connect to your battery's positive terminal needs to have an appropriately-sized fuse, placed within a few inches of the terminal.  If the only thing damaged was your new wire, then you've been very lucky.

Answer 3

Most likely the wire got pinched when you were re-installing the radio. It was glowing orange becauwse it was shorting out and you didnt have the proper fuse on the wire. Also, there is no reason for you to have to run directly to the battery, as you could just go to the steering column and tap 12v there and fuse the wire. This happens sometimes when re-installing equipment, but you should definately fuse the line next time.

Cheers