After looking for almost 2 years for a decent used pick up truck for yard clean up, I found a nice Ranger XLT with the 3.0 V6 with every option and they all still work including the AC.
I made one trip to the store, got home and loaded up some branches to haul away, when I started the truck, I started smelling smoke. I shut it off, and realized I had smoke coming from under the hood. The altenator had smoke just pouring out of it. I quickly grabbed a pliers and took off the negative cable and in time the smoke stopped. I then just tapped the cable to the battery terminal and by the spark I could tell there was a large current draw! The altenator started to smoke again also.
I put a new altenator on and everything is fine so far, no heavy current draw and the voltage guage is reading a little higher than it used to when running.
Do you guys think this could have lead to a full blown fire? I have to admit I am a little paranoid now, what ever failed in this altenator could happen any time on any vehicle.

Well, that stuff happens. Alternators short, batteries short.....that's just the way it goes. I wouldn't worry, as the odds are that it won't happen to you again.

Gene

Good thing you caught it quick! Batteries put out a lot of current.

Doug

Usually the only things that fail in alternators are the diodes and bearings.. well bearings can fail in anything with a pulley, but usually they only fail in the sense that it will no longer charge your battery. At one point in time someone could of replaced it with one that had a smaller amperage, then what it needed. Which that will eventually cause a failure. The only scenario i can think of is that something in the alternator probably the diodes failed and caused a short, which caused the excessive current draw.. A full blown fire may of been possible, but not very likely unless you had over heated wiring for an extended period of time or a short across the battery.

Yes, you WOULD have had a full-blown fire and likely a battery explosion. It sounds like you got to the alternator just before it developed too much of a short. The integrity of the windings can only last until they get hot enough to smoke the insulation. Once they've smoked a good bit, they are astable and they can short enough to catch on fire. It's only a matter of time, whether seconds or minutes. Unforuntely, copper has the highest melting point of anything on the vehicle so the circuit won't burn open until everything else has been crisped.

To those of you who are thinking of spewing "BS!" and "HORSE MANURE!" at me now, I've seen foot-high flames out of one of those babies before....

No Nick, I agree. As has been already said, batteries put out a lot of current and a dead short in the alternator could have been, and almost was, disastrous. I would suspect a cheap replacement alternator though and this happening is not really that common. If the underhood wiring between the battery and alternator are OK, replace the alternator and you should be good to go. Buy a good one though.

Tricky thing. While the battery is discharging at a high rate, and kicking hydrogen,
you must disconnect a cable, and hope the battery doesn't explode before you're done.
Throw in a few flames for drama. Happens fast. No time to ponder the melting point of copper. My last short was on a farm tractor. Near the gas tank of course.

Glad you saved the day Scott. Not that common of event, but it kicks your heart rate up a bit
when it happens!

Ford's alternators (the 2G, *I think* ones) in the 90's were notorious for posing a fire risk. If your truck was made after 1999-2000, it should have the 3G alternator on there, which does not pose a fire threat any more than a normal alternator would.

^^^^^^^ Yup what William said, common problem on the 2G internal regulator alt that has the quick disconnect battery plug, if you have one of those it should have came with a new plug...

The problem isn't so much alt failure, it's the plug that develops resistance and burns up under load when charging... Often burn after battery was partially discharged due to radio being played, lights on, etc....

Tom