Hello,
My truck is ford f150 1994 6 cyld.
Ladt monday altnerator caught alot smoke and become fire so replace new alt and wires.
I wonder is it normal for back of altnerator
getting warmer or almost hot I probe tempature is 250 c.??
Thank

 

It's unusual for an alternator to burn. Normally, the diodes just quit working. The most likely way I can think of that would cause an alternator to literally burn is that there was a short that caused it. Maybe the wiring harness was bad.

I don't know about the temp of a properly working alternator, but I'd have to say 250ēC sounds high. Is this the new alternator? If the air coming out of the alternator isn't hot and only the back is, I'd have to guess that it has a bad bearing in the back. Do you hear any unusual noise coming out the alternator?

 

Thx for post and i find solved. I called Paul from my area he working for starter and altnerator. I asked him about back of alt. He said it is normal for warmer or little hot
that it is as heat sink (rectifier). He said it approx to 300 f degree. I asked him what it cause smoke and fire. He said that harness loose make arc make heat up. So he working alt for 20 years. He know alt as well. So now I understnad. I put electric grease on both connect to alt what he said to prevent it from arc. I remember I replace once that harness too dry that how happened .
Thank for post .

 

I guess your alternator must have been pumping out some amps at the time to get that hot.

Good to hear you figured out what caused the original fire. Hope it doesn't happen again!

 

Loose connections (anywhere) create increased contact resistance. Heat is produced as current flows through this resistance. Add enough heat and you have Fire! The grease is a good idea and I would recommend it too. Just don't over do it. Only the contacting surfaces benefit.

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