alternator noise, help!!!!

3.2Carrera · 3.2Carrera's Garage

When i turn on my car, my alternator is fine and makes no noise, but if i turn on the head lights or roll up the windows or turn on the A/C, then the alternator will start make a squealing noise, the noise is not to loud, but i want to to go away. When i turn off the lights or turn off the A/C then the noise stops. The car has 75,000 miles, is it time to get a new alternator??? Any suggestions?? The noise is definitely coming from the alternator and the fan pulley area.

Thanks !!!!

scottb · 10-14-2007, 08:31 PM

It sounds like the alternator is going south and when you put a load on it the bearings start squealing. Do you have any other symptoms like the lights getting brighter when you step on the gas, or your tach jumping? If so, then it most certainly is the alternator.

I had mine rebuilt by Foreign Alternator & Starter in Northridge. It's a little hole in the wall place, but they did a good job and several years later it's still going strong. I think I paid about $85.

Good luck.

3.2Carrera · 3.2Carrera's Garage

The lights are fine and the tach is fine to .I live in sherman oaks, so i will bring my alternator to that place and just have it rebuilt, i know alternator's usually go out at about 80-90,000 miles so i guess it is time, so you paid about $85 to have it rebuilt, that great because a new one is like $500.

Jim Sims · 10-14-2007, 08:43 PM

Maybe first you should check belt tensions.

2.7RACER · 10-14-2007, 08:48 PM

As usual Jim is all over it. Worn or loose belts squeek. Bearings vibrate. Time for a new belt.

3.2Carrera · 3.2Carrera's Garage

I did check the tension of the belts, and i experimented with some different tension settings and the noise was still there, and the belts are almost like new.

450knotOffice · 450knotOffice's Garage

My guess is still the belt slipping on the pulley. If the tension is, in fact correct, it is still possible for the belt to slip during a high load situation as you described. It can be due to poor belt quality or even possibly due to a slick pulley surface.

The more electrical load you put on the alternator, the more drag it produces. It seems odd, but it's true. So, as more load is applied to the alternator, the harder it becomes to turn and the more likely the belt is to slip, causing a high pitched squeal.

3.2Carrera · 3.2Carrera's Garage

so should i just try a new belt?, and see what happeneds, and you know now that i think about it, I did just get my fan and sourding area re-painted, so I have a new pulley on the alternator blade, could that be a factor? and the noise only started when i put the new pulley on. I have had the car for 7 mounths and in the first 4 mounths that I have had the car, there was no noise when eletctonics were used, but after the repainting process and new pulley, the noise came .I will post a photo...

3.2Carrera · 3.2Carrera's Garage

see.... all new pulley and shim's.

450knotOffice · 450knotOffice's Garage

Yea. I see that. The belt is very possibly slipping on the new pulley surface. How many shims do you have on the rear side of the pulley (under the bolt)? For mine, and with the particular belt I'm using, I needed no shims on the front side, so therefore, all six on the back side (under the bolt). You want that belt TIGHT. No more than 1/3 to 1/2" max deflection in the center when pressed by your finger.

3.2Carrera · 3.2Carrera's Garage

I have no shims between the alternator blade surface and the pulley. All 6 of my shims are on the front of the pulley surface, between the pulley and the bolt. The bolt that goes on the pulley surface. I am not a 100% sure that i have 6 shims, but my belt from the crank and the alternator is pretty tight.

3.2Carrera · 3.2Carrera's Garage

when u say under the bolt do you mean between the alternator blade and the pulley or on th surface of the pulley, under the bolt

rnln · 10-14-2007, 11:34 PM

squealing noise? Is it a mechanical noise or electrical noise?
I am not sure if this is related but maybe so I put it up anyway. My car used to be fine, on this area, but lately I sometimes heard similar noice (mechanical noise) at start up for couple second than it goes away. The recent changed before this noise appear was increase the tension of the fan belt. Before I increase the tension of the belt, I have never heard this noise. Maybe you want to double check your belt tension to see if it's too tight.

450knotOffice · 450knotOffice's Garage

(Sorry for the late response. I was watching a movie.)

rnln, I suppose that is also possible. 3.2Carrera, how much deflection of the belt do you have at mid-span?

As for my shims...I have no shims between the fan/alternator housing and the pulley half that you slide onto the alternator shaft. All of mys shims are under the bolt. In other words, when I put the pulley system together, I slipped on the pulley half, then all six shims, and then the bolt.

If the belt tension is good, then I suppose you could remove the belt and spin the alternator shaft. If it spins freely, with no grinding or drag, then you could remove the alternator and bring it to an alternator repair facility to have it bench tested.

One other thing you can do is check your alternator voltage output. If you have a Voltmeter, check the voltage between the positive and negative battery posts with the engine off. You should get somewhere around 12.6 to 12.8 volts, possibly as high as 13.2 max (if it's been charging for a while). With the engine running and all of the car's electrical accessories on (lights, radio, Air Con, etc), check it again. You should get somewhere between 13.8 to 14.5 volts. Higher is bad (overcharge) , as is lower.

3.2Carrera · 3.2Carrera's Garage

I currently have the same shim setting that you are talkimg about. All 6 shims then the bolt. I am going to take the whole thing apart and i will try spining the alternator and so if it makes a grinding noise or if it spins freely. If the alternator is fine then do you think i should try a new belt and/or a new pulley?

RickM · RickM's Garage

Many years ago I had a similar situation. I fiddled with the belt, shims and alternator to no avail.

Here's what I found:

On the face of the fan is the "key" that the pulley half fits over....figure A. The pulley half was either not installed over the key properly and/or not secured tightly enough and it cut a groove into/around the fan's key...figure B - key side view w/ groove in red. As a result the pulley would slip no matter how tight the nut was torqued.

To solve the problem I opted to buy a new fan from the factory and replace. However, it was likely repairable.