Alternator set on fire

Bri

Bri

New member
I have a '97 SR5. My 100A alternator fuse blew a few days ago. I looked over all of my wiring and couldn't find any shorts (heard an O2 sensor short can blow that fuse). I decided to replace the fuse to see if it was just a fluke. Did that today and about 4 seconds after I connected the negative terminal to the battery, the alternator went up in flames right at the wire on the terminal (not the engine harness wires).

Since the car wasn't running yet, I'm assuming the short is in the alternator itself. Does this sound right? Anything else I should check before swapping the alternator for a new one? Wouldn't want to set the new one on fire too if the short is somewhere else. Also, it's scary as hell when you're in a parking garage below your apartment and not expecting it. :target:

Thanks in advance.

edit: also, think I could get away with just replacing the voltage regulator? broke college student just trying to make it home so I can start work next month.
 
Last edited:
Register to hide this ad
A short in the O2 sensor wire will blow the efi fuse. You could check the resistance of the alternator positive wire to ground. If you have 0 ohms there's a short in the alternator itself. Not sure about the voltage regulator. Sounds more like a diode issue.

Good luck
 
I know it's apples and oranges, but I had almost the exact same experience with a Challenger. I was actually changing plugs on the car, obviously it wasn't running, key wasn't even in the ignition, and smoke started pouring out of the alternator! By the time I yanked the battery cables (not quick or easy) the wiring on the alternator's back was melted and the thing was actually on fire! None of my mechanic buddies would believe me.

I replaced the alternator, repaired the burned wiring, and never had another hiccup out of it - I have no idea what caused the whole fiasco, but just replacing the alternator seemed to remedy it. And you're right, it scared the geebus out of me too! :scared:
 
Skidmarcx said:
If the alternator smoked that pretty much settles it... I'd do the big 3 upgrade while you're in there
Click to expand...

cool, thanks. never heard about the big 3, I think I still have some 1/0 welding cable left from the battery relocation in my Honda so I'll probably do that.

hambob said:
You could check the resistance of the alternator positive wire to ground. If you have 0 ohms there's a short in the alternator itself. Not sure about the voltage regulator. Sounds more like a diode issue.

Good luck
Click to expand...

I should've thought of that. I'll probably swap the whole alternator then, not worth risking a fire just to save 150 bucks now.

Nachtjager said:
I replaced the alternator, repaired the burned wiring, and never had another hiccup out of it - I have no idea what caused the whole fiasco, but just replacing the alternator seemed to remedy it. And you're right, it scared the geebus out of me too! :scared:
Click to expand...

thanks for the input. I've definitely had my share of problems that were completely unrelated to the job I was doing. my distributor went bad when I was changing my clutch somehow. took me forever to figure out.
 
Basically upgrading (B+ to alternator)(B- to chassis)(B- to engine block)... You got the right idea using welding cable

I usually add a fused circuit for B+ to alternator and leave the factory circuit alone
 
yep, pulled out my multimeter and there's absolutely no resistance between the alternator terminal and my neg battery cable. thank god for fuses. :thumb:
 
Wow I'm glad I installed that 100 amp breaker when I did the big 3 install.

Note to self ... Time to buy a CO2 exinguisher.
 
You must log in or register to reply here.

Members online

Total: 215 (members: 2, guests: 213)

Forum statistics

Threads
278,306
Messages
3,554,046
Members
248,016
Latest member
Advally Service

Share this page

Trending content

Back
Top