I was trouble shooting the cause for a small fire at the base of a new alternator. I found fried wires and I am having trouble getting the correct replacement. Can someone please help me with this? 

When I followed the wires down they go into the bottom of the fuse box into a black port. I also found they had been previously spliced and I am not sure if this is aftermarket or how it comes. 

Yes they go into the fuse box in the engine bay.  Hit the yard and pull a good set.  Something caused the overheat.  Big Amp?

That is factory. The heat/fire is from a poor connection at the stud. 

GD

yeah, looks like corrosion at the connection and maybe up under the insulation created enough resistance to really heat up!

On 7/16/2019 at 1:00 AM, GeneralDisorder said:

That is factory. The heat/fire is from a poor connection at the stud. 

GD

Quite possible. 

Or maybe twisting of the stud from overtightening, without a backup wrench underneath.

Or just a crappy Alternator.

I'd replace the Alt and the wiring.  Can't trust that Alt after that much heat through the circuit.  An actual fire!  Wow.  Seen the wires cooked but never actual flames.

I had one catch fire on me. Customer dropped it off overnight with a charging complaint. I go out to check it - sure enough it's stone dead. Grab my jump pack with the intention of a test run and probably drive it around to one of the bays. Starts up, and immediately sparks start shooting out of the back of the alt and something inside is glowing red hot. I hurry around and turn off the key. When the fan on the alt stops, I get about a 12" flame leaping out of the thing. I about $hit my pants of course..... I did manage to (barely) blow out the fire and was left with a smoking, melted alternator.

I've run a lot of safety meetings and been party to many more. Never has anyone mentioned the need for a fire extinguisher when performing a jump and basic charge test. But yeah - I would have to say there is cause. 

GD

On 7/15/2019 at 8:06 PM, wildhrt98 said:

I was trouble shooting the cause for a small fire at the base of a new alternator.

is it brand new OEM or aftermarket new?

Yes, it does make a difference.

Most parts store alternators are not "new" - they are remanufactured - and have a high failure rate within the first year. If it is a parts store unit with any kind of warranty - take it back, get your money back (as much as they will give you) and invest in an OEM unit - even a used OEM one from a junkyard is preferable to the aftermarket ones.

I caught my alternator harness before it caught fire, quit charging during a drive, tried to jump it, and then we noticed the alternator stud over was weirdly bulging away from the stud, pulled it off it was a short fire waiting to happen... so i walked to Ace Hardware and bought some electrical wire, electrical tape, etc and re did my own line from the alternator back toward the fuse box to get home, the next day i took a OEM alternator from the junk yard as well as that harness...
I didnt use the alternator, or harness, but i have them for backup, i ended up doing a really solid job on my my make shift harness, and i replaced the stud and part of the housing etc... but still... this isnt an uncommon problem i believe.