how do i know if my Alternator is bad or the bearing?

[MercNasty]

There is a squeaking noise almost sounds like a bird chirping, it doesnt quite sound like some of the bad alternator videos i have seen online. Im working on getting a video put up so you all can actually hear it. My mechanic says he THINKS it may be the alternator but he isnt sure and he wants to take everything apart. Whatever it is I want to get it fixed this week.

[MrBluGruv]

Most times I've had a bad alternator, you could feel it in the pulley by spinning it by hand. Try loosening the serpentine belt off the alternator and spinning the pulley, if it squeaks by hand you'll know that's where to start.

[MOTOWN MARAUDER]

depends on your definition of "bad" meaning just sqeaking (likely the bearing), or is it not charging your battery?

[martyo]

It can also be the idler that squeaks.

[fastblackmerc]

Originally Posted by martyo

It can also be the idler that squeaks.

Either the idler or the tensioner pulley(s).

[martyo]

Originally Posted by fastblackmerc

Either the idler or the tensioner pulley(s).

Yes true -- I should have send that!

[EMAS]

I'd say find another mechanic first and foremost. There is no excuse for "thinking it's the alternator" and wanting to tear it down. It just takes a couple of seconds to remove the belt and inspect each pulley and alt.

These cars also have a one-way clutch pulley on the alternator. Have an assistant rev the engine to 2500 and shut it off while you observe the alt and listen for the noise. If it continues after shut down it could be the pulley or the alt. With the belt off turn the alt by hand in both directions if it makes any noise or has any roughness if it does in both directions then it's likely the alt bearings if it only does it in one direction it is the bearings in the clutch pulley. With the belt off spin each of the idler/tensioner pulley as fast as you can by hand if it takes more than a second or 2 for it to come to a stop it is time for replacement. Also feel for any wobble, looseness or "rough" feeling. The pulley is available separately but you need special tools to R&R it but it can be done on the car. You should also inspect the belt for any imbeded sand or grit in the grooves, it will look like little shiny spots. A bad tensioner can also be the cause or the chirp. With the belt on and engine running with all accessories on high watch the tensioner arm if it is bouncing around then it is due for replacement.

[MercNasty]

All of this sounds great and I wish i knew how to take the belt off to inspect, but that is something i have never done before. I will make a list of things to check and take it to my mechanic, he isnt going to charge me anything to figure out what it is but he wants me to leave the car over night. NO WAYYYYYYYYYYYYYYY

[MrBluGruv]

That's actually really easy if you have a ratchet, but would probably require a picture if you've never done it before. Basically, all you need to do is pull the tensioner back (for the Marauder, if you're at the front of the car looking at the front of the engine, that would be pulling it to the right) and slip the belt off of at least one pulley. I'd recommend slipping it off the alternator pulley as a matter of fact, it's the easiest on to reach IMO when you go to slip the belt back on the pulley. You can use the ratchet without an attachment on it by putting the peg into the square notch on the front of the tensioner and pulling.

Believe me, once you try it and succeed, you'll see what I mean by ez-pz.

[Chevyguy]

The alternator actually has the SAME bearing inside the case that is used in the idler pulleys. This can screech and howl while the alternator still puts out proper voltage.

This can be replaced (what do you think they do when you give them your core?) but usually just replace the alternator instead.

[EMAS]

As I said before find a new mechanic if he wants you to leave it over night for a 5-10 minute inspection.

As MrBluGruv noted all you need is a ratchet or breaker bar. The diagram for the belt routing and instructions on which way to move the tensioner is on a sticker under the hood, or at least there was when it left the factory.

[MercNasty]

Ok guys thanks for all the input, tomorrow I will be taking the belt off and inspecting the alt, idler and tensioner pullies. I will report back tomorrow with the findings and to receive instructions on what to do next. Im hoping this is something that will be a cheap fix. Also should i replace my belt with a goodyear gatorback belt?

[MercNasty]

Ok so I hadnt been able to take my belt off and inspect the pullies and alternator but earlier today I was in my mechanics neighborhood so I stopped by and had him look at it again, The very first time i took it to him about the noise a few weeks ago, he said it was the alternator now today with me mentioning the tensioner and Idiler, he said its the tensioner and wants to charge me $450 to fix it. I am going to take it somewhere else and get a second opinion because he didnt take the belt off or anything he just rev the engine a few times and said it was the tensioner. I thought this guy was a good mechanic and he likes MM so I figured i could trust him. He has done good work for me in the past but Im not to sure about him this time. What are some of the signs that it could indeed be the tensioner? Im not having any problems driving the car its just a loud noise that appears to coming from somewhere around the alternator. Its like a mild squeak/squeal. Please help

[a_d_a_m]

Originally Posted by MercNasty

Please help

OK. As others have said, the solution to your problem is quite easy. You just need to

Originally Posted by MercNasty

take my belt off and inspect the pullies and alternator

Which you haven't yet done.

[boatmangc]

Just take a can of CRC 6-56 or if you can't find that WD-40 and with the car running and the pulley squeaking, spray a SMALL amount of the product directly on the shaft the pulley runs on (use the straw that comes with the can).When you spray the shafts a small amount of the lubricant will be wicked into the bearing, they will get quieter as soon as the lube hits them.

You will quickly find out which pulley it is, it is most likely not your alternator. If it is alternator the squeak will not go away or get quieter when the pulley shafts are lubricated.

And for sure as has been said several times in this thread, find a Mechanic, ask around and find out who your neighbors/ co-workers are using, go with someone with a good reputation.
Sometimes a shop that charges a higher labor rate ends up being cheaper in the long run.