ok, so the truck was running, i drove it about 4 blocks and smelled something so i popped the hood and my alternator was literally on fire! what would cause this? it seems like as soon as i get one thing figured out another happens. the whole truck is gunna be new by the time its usable. any thoughts as to why this might have happened would be great so it doesnt happen again, unless the alternator was just at the end of its life but ive never had one start on fire. lucky for me i caught it before it did damage to anything else...

thanks,
jesse

 

Good god...faulty wiring I'd say. If you only drove it 4 blocks you obviously didn't get it super hot. Sounds like an electrical arch in my opinion.

 

Surprised PCM didn't cut power to it. Isn't there a fuse for alt also?

 

i tried calling a buddy a minute ago who repairs alternators. he told me a rectifier or diode? went bad or got too hot and it was pushing too much current? does this sound right? and i might not be repeating that 100% correct

 

A rectifier is a couple of diodes tied together to change alternating current to direct current (AC to DC). They also act like a check valve to keep current flowing out and not back in. If they fail, you can get overcurrent, open circuit, or send alternating current out of alt. All of these are bad. I have burned up alternators before, but never had one catch on fire. You may be lucky and only have to change alt. I would check all wiring at dist block to be sure before I installed a new one.

 

Wow man, fyl! lol

Just kidding; while I've never caught one on fire, I've worn out a few prematurely by making them work too hard. Sounds like yours might have met an early death from all the recharging it's been doing because of all the cranking you've been doing because of your ignition problem.

My auto electric guys have drummed into me that alternators are for keeping healthy, fully charged batteries fully charged. I make it a point never to jump a dead or low battery and make the alternator recharge it. It's always best to charge it with a charger, then make sure you know why it ran down.

Anyway, just slam a new/rebuilt alternator in there after fully charging your battery and you should be good to go.

Hang in there, I think you've used up all of your bad luck.

 

yeah im not so sure my bad luck does run out... none of my wiring for the alternator was touched other than disconnect/reconnect when i did the heads, and it all looks ok. nothing melted in the underhood fuse box (pdc?) is it safe to assume that it was in fact the alternator that was in fact the culprit and not something else crazy? the truck isnt really parked optimally in the driveway, but it sits where it is until i can get it fixed...

 

Well, if it wasn't bad before.... it probably is now.....

Did you happen to notice what you output voltage was before you discovered the fire?

 

No clue what the output voltage was. As soon as i saw it i yanked the battery cable and put out the fire. Didnt have anything with me to check anything

 

PCM controls the field windings for the alternator....... One terminal should get 12 volts (via the asd relay, so, only for a short time, unless the engine is running), the other terminal is grounded by the PCM. Might wanna verify that wire isn't grounded out somewhere else.....