Ok here is the scenario.

'97 f150 XL V6

Coming home from work friday night I notice the guages are dim. Soon the battery light comes on. Make it home no problem. Saturday I pull the alternator. It is grinding, and metal bits fall out. For *****s and grins Ihave it tested. It;s bad. I buy a new one. ($170 for an alternator) After I regain my composure I put it in and everything is fine. Or so I thought.
This evening comeing home from the movies, guages are dim, battery light not on, but the electrical guage is all the way to the bottom indicating dead battery I assume. I make it home ok.

The battery is about 18 mos old with 23k miles on it.

Any ideas? I am going to have it checked out tomorrow. Hoping I didn't get a bad alternator and hoping my battery is OK.

 

I do not know if it applies to F150's but the battery should be charged when it gets very weak or is dead. Some of the alternators made today have plastic in them and the alternator can be damaged if it is used to charge a dead battery.

Please post the results of what is found. Thanks and good luck.

 

I recently had the same problems (dead alternator), and temp1 is correct. I bought an alternator from eBay ($20) and had a local alternator shop replace the housing so it would fit in my truck (it was for a 91 explorer - I have a 94 F-150). The guy at the alternator shop told me that if the battery was not charged enough, the alternator would have to work too hard to charge it. This would result in massive heat that would kill the alternator. He also said that, generally, if your battery is charged enough to start you're truck, you should be okay.

Other posts that talk about an alternator going bad over and over again often end up with the wiring harness being at fault.

Oh, the local alternator shop rebuilds alternators for around $90. Maybe you could check into something like that in your area.

 

THanks for the help guys. I ended up replacing the battery and it seems fine for now.
The weather has been so nice lately I have been riding the MC and giving the truck a rest. $2.30 a gallon gas prices are another good reason!