Noisy Alternator??

[Joe/Ct]

I have developed a squeak upon start-up, that goes away after a couple of minutes. I suspect that it is my alternator, but can't be sure. How can I tell? What is the failure mechanism, catastrophic or gradual? How tight should the belt be? If it is the alternator, can it be repaired or must I replace it?

[Ronnie]

Start it with no belt to confirm noise.

[PeteVS]

You can use a mechanic's stethoscope or a broom handle. Press the end of the broom handle on what you think is making the noise and press your good ear (I'm assuming you're like me and only have one) against the side of the handle. You'll hear all the noises coming from that item.

[chuck stevens]

Joe I don't know what you have, but my GM one wire with a wide belt makes a lot of noise too. I thought it was the bearings and changed them- noise still there. It has the alum., pulley and I think the noise is the belt working on the pulley. Don't tighten the belts too tight or the water pumps will wear out. A friend has a Honda alt., that is quiet and works good, but I don't know what year it is. Chuck.

[Joe/Ct]

Originally Posted by PeteVS

You can use a mechanic's stethoscope or a broom handle. Press the end of the broom handle on what you think is making the noise and press your good ear (I'm assuming you're like me and only have one) against the side of the handle. You'll hear all the noises coming from that item.

The trick that my Dad tought me was to use a screwdriver, with the blade touching the part and the fat handle end to the (good) ear. I did that to the alternator and hear lots of noises.

[Joe/Ct]

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Originally Posted by chuck stevens

Joe I don't know what you have, but my GM one wire with a wide belt makes a lot of noise too. I thought it was the bearings and changed them- noise still there. It has the alum., pulley and I think the noise is the belt working on the pulley. Don't tighten the belts too tight or the water pumps will wear out. A friend has a Honda alt., that is quiet and works good, but I don't know what year it is. Chuck.

I was told that I had a three wire GM alternator (I don't know the difference between it and a Ford alt). I wouldn't be concerned, except the this squeal just started the last few days. I think that I will try some belt dressing to see if that helps (it is a new belt).

What is the best way to tell if the belt tension is OK? On one side of the alt, it seems a little tight; on the other, OK.

[Bill Steiner]

It could be the belt , but I would not use belt dressing. Bill

[Labold]

Anxious to hear what you come up with. I have the same problem with mine. Sometimes it is noisy and other times it is quiet. I installed a new alternator and the same noise came back. I am using the big pulley on mine as well so that the wide belt that is used on the water pumps will work.

[Chris Nelson]

I thought I was the only one with a noisy one wire alternator. It drives me nuts to hear it. I took the belt off and sure enough, it stopped the noise. I listened to the water pumps with a stethoscope and they were quite. The alternator seems to be the problem. I took the alternator off and it has needle roller bearings. The shaft had marks from the rollers. My reaction to that was, "WHAT THE HECK? I was in the bearing business years ago and needle rollers are not intended for speed, such as an alternator. Ball bearings are designed for speed. So what gives with needle rollers in a high speed shaft like the alternator. Sure beats the heck out of me. Maybe someone here has some insight into this. Regarding using belt dressing, don't use it. It will just compound the belt problem. It is a temporary fix at best.

[296 V8]

Cant be the alternator, V8 's dont have em

[Joe/Ct]

Well Guys, I removed the alternator with the intent of having the bearing replaced. The guy that I brought it to said that the alternator was OK and that maybe the squeal was too loose a belt. He also noted that, along with the rest of the alternator, the inside of the pulley was chromed. He suggested sanding the inside with 150 paper. I thought that was a little heavy, but did use 400 wet paper. I reinstalled and now the noise is gone and all seems to work OK. Thanks for all the help and suggestions.

[G.M.]

There isn't anything in an alternator to make noise other then the bearings and some have internal fan blades that could rub on the houseing or windings.There are small brushes but I don't think they would make noise. Remove the fan belt and spin the pulley and you will feel or hear a bad bearing or blades rubbing. I see you found the pulley noise as the problem. G.M.

[gmc1941]

With no load on the bearings they will sound quiet. Unless they are really crap. Fan belts are make with a seam and sometimes if you watch ( from a distance ) you will see the belt rise and fall in the pulley. Change the belt and try and find new belt, they do dry up. Good luck