I have replaced the alternator on my 1996 Pathfinder 3 times in the past year. Each time it starts to squeal constantly after a few weeks, and then eventually it won't charge the battery and the truck stalls if I turn on the blower motor or defrosters. I have tried three different brands of alternator, and the voltage regulator is built in to the unit. Does anyone know what the problem could be?

Might be the pressure plate .

I would suspect the belt tensioner is going bad.

Either the belt has stretched, or the tensioner is not keeping it tight.
Or it has oil on it.

the noise is the alternator belt, what maybe going on is you need an alternator. it could be that there is a bearing that is ceasing up when it cools down and when you start it up it takes a min. to get spinning and this is causing to much drag on the belt and making it squeal.

The squeal is coming from the alternator belt, When the temp is low, the belt is hard and glazed and lost its ability to create friction.

check the tension. cheap belts will stretch. if after you retension them (especially the alternator belt) you may need to replace them with BANDO or OEM belts.

replace the charging relay

Hello, this to me sounds like your fan belt slipping (not timing belt). To adjust the fan belt you need to undo your bolt on the alternator, pull it tight onto the fan belt and while holding it tight do the bolt back up tightly. this will stop yoour fan belt from slipping. I hope this helps.

Have you tried to checking the tensioner and the idler pulley? The idler is a fixed pulley on the driver side of the alternator. Most of the time this gets rusted during sudden change in the weather or its just the bearing inside it just worned off.

Shortly after replacing the serpentine belt in my lancer, the same thing happened. It is NOT the timing belt. Belts squeal when they slip. If your timing belt slipped it would cause your car to run funny.

have somebody check the belt for wear (or do it yourself), replace if necessary. If it doesn't need replacement, just tighten it.

If you have the 4cyl engine that I have, the tightening is kind of a pain in the ****. Not a great design by mitsubishi. There's a pulley near the front right corner of the engine in front of the alternator. the belt should be running around this pulley GROOVE SIDE OUT. This is the tension pulley.

To tighten:
1) Lightly loosen the bolt in the center of the pulley (slightly loosen, DO NOT REMOVE).
2) Under that pulley there's another bolt. You can see that the bolt goes through a piece of metal
attached to the back of the pulley. Figure out which way you need to turn the bolt to move the
pulley toward the front of the car. (i don't remember if it's right hand thread, or left hand) This
puts extra tension on the belt. You probably don't need much. Over tensioning the belt can
cause pulley bearing failure. If you haven't done this work before, ask someone for
help. It's better to tighten a little bit, a few times rather than overtighten once.
3) Don't forget to ReTighten the bolt in the center of the pulley.

If there's lots of cracks and pieces missing on the ribs or grooves of the belt you should replace it first.

Happy repairing,
Cliff