Leaping Lizards, my car's on fire

Yesterday I dropped my car off to the local tire store to have them fix a slow leak. It was supposed to take about an hour so I walked next door to get a haircut and returned about 40 minutes later. Soon after I returned the sales clerk ran in yelling for me to get out to my car - “IT’S ON FIRE”. Amazingly calm, I manually unlocked the car which of course set the alarm on, popped the hood only to be greated with a small fire that I actually just blew out - The insulation on the wire connecting my alternator to the battery was, uh, toast, along with a vacuum line.

I quickly rationalized that the insulation must have rubbed off and this positive wire touched ground which caused the fire. On reflection though, that couldn’t be the answer. Virtually all of the insulation on this wire was burned off - but the wire was not touching ground, anywhere. The battery was not warm from drawing too much current - just that one wire was damaged.

In the interest of full disclosure I did change the alternator about 1000 miles ago.

So the question is - what would cause this cable to catch fire. The answer should explain why it took at least 40 minutes to happen and why even after the insulation was burned off the cable was not shorted to ground.

Any ideas would be appreciated.

Car details:

1997 Camero, Red


137,000 miles.

this incident happened after I had driven approximately 1 mile in very mild (50 degrees)temperature. (Mild for Cincinnati in February)



Could be an internal short in the replacement alternator that overloaded the wire. I would immediately check for a dead short at the battery terminal of the alternator before replacing and reconnecting any wires.

Whoops! Too late. I’ve already replaced the alternator wire and am driving again. No problems. That is why I posted the question - after I thought about the circumstances they didn’t add up and I guess I’m a little nervous.


Then, it had to have been the alternator wire chaffing and shorting, despite your observations. Happy motoring!

How could the clerk have seen the fire with the hood closed if the fire was so small “that I actually just blew (it) out”?

He saw the smoke, lots of it (he said)and assumed fire. When I popped the hood their was some smoke but not much. The fire had consumed 1 plastic vacuum line and all of the insulation on the alternator cable.