I just replaced my original 130amp alternator on my '97 F150. I replaced it with a NAPA Premimum 130 amp. I started the truck when I done to make sure all worked ok. After about 5 minutes I shut it off and noticed a burning smell from the engine. It was coming from the alternator. The alternator was so hot I could barely touch it. Is it normal for the alternator to get this hot?

 

No, they should not get that hot. A little warm maybe but you should be able to put your hand on it and not have to take it off at all.

Sounds like it could possible have a bad core, or maybe binding slightly. Before you put it on could you turn the rotor or shaft easy? I would have it replaced because if it is getting that hot it is defective.

 

It spun very freely before I put it on. I tried it again today and it seemed to not get as hot. I did charge the battery overnight, so that might have helped. I took the battery to Sears and they checked it. It was a 870 CCA battery and it tested out at 875 CCA so I am assuming the battery is good.

 

One other question - ae you sure you originally had the 130 amp alternator or did you have the 95 amp? My NAPA partsman had a message pop up on his monitor when I replaced my alternator this weekend. Seems they have had a few cases of people replacing the 95 amp alt at this shop with the 130 and frying the wiring harness shortly afterwards.

Otherwise, my new 95 amp NAPA alternator went in fine and runs cool. Also replaced the Serpentine Belt as long as I was in there on the '97. It was the original, and a bit worn, but still serviceable. I hadn't replaced it before since inspection showed it to be fine. Not too shabby fopr 160,500 miles! (Same for the alt!)

 

My alternator is always hot. I too replaced mine with a NAPA last year sometime. Mine still works fine and have had no trouble. The only problem I had with it was that the pulley had a small dent in it. The laternator gets hot enough that I cannot touch it but not hot enough to fry an egg on so to speak. I just assumed that since the alternator sits on top of the engine it gets allot of the heat generated from the engine. BTW, I build new alternators for a living and I don't believe the heat will hurt anything.

 

I did some more research and apparantly this is normal. When they changed from an external fan to the fan being mounted internaly they started running hot. One guy I talked to said that he replaces GM alternators 3 times as often as the FORDS so it is a problem with the design not the manufactuer.

Hope this helps