Belt squeal (while accelerating)/alternator question

[dec322]

Hi all! I have an 84 scottsdale with a stock 305. I have been fighting with a squeal that is most pronounced during acceleration. I bought this from a buddy in a different state and have owned it about a year. The squeal would come and go but now it's here to stay. Here is what has been done:

1. New belts before I bought it. I'd guess the truck has around 5k on the belts

2. Checked tightness of belts. I can twist them 90 degrees but cannot pull them on any of the pulleys

3. The battery gauge in the truck moves when it starts to squeal but I didn't notice much of a different on the multi-meter (probably need to test again)

4. It sounds like it is coming from the alternator. The one in the truck is 66 amp from 2002 so I replaced it. I bought a 78 amp rebuilt unit from Autozone (running a new head unit, 2 channel amp, 6x9s and powered sub....installed last week). The fan on the unit looked like it wobbled when you spin it. It was tight but the fan had a wave about it. I installed it to see and the squeal was the same. The alternator pulley/fan was hot and the belt was hot (only ran 45 seconds).

5. Today I replaced the new one (installed yesterday) with the 94 amp unit from O'riellys hoping that the fan was bent and that was the cause of the squeal. The sound is the same. The pulley gets hot and the belt gets warm.

Is it possible it's the alternator and I got two bad ones? I wouldn't think it should be getting hot...especially after running only 45 seconds.

I'm about to start eliminating belts (within reason) to see if I can narrow it down.

 

[fast 99]

Picture of belt and pully arrangement please. Have seen mismatched pully diameters.

 

[Buck69]

The heat indicates it is the location of the squeal. A commonly overlooked problem is with the pulley itself. They wear out. The belt should be supported by the sides and not sit deep in the pulley.
Have also seen where someone had installed too narrow of a belt at one time and parts stores keep replacing it with the incorrect matched belt. The belt will sit low in all the pulleys in that scenario.

 

[Snoots]

Like @Buck69 said, get a slightly wider belt.

 

[dec322]

Thanks for the input. I’ll post pictures tomorrow. The squeal is happening with 3 different alternators (and different pulleys) but the same belt.

I read somewhere that you can disconnect the alternator and see if it eliminates the squeal/heat. This is supposed to differentiate between an electrical prime and mechanical problem.

 

[dec322]

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[Buck69]

When you say you have tried different pulleys, were they used?
Take a look at the depth your belt is sitting at on all the pulleys. It looks to me like the belt is sitting too deep in the one for your alternator. The running surfaces should be straight and the belt should be sitting at or at least very close to the top of the V.
Sorry, didn't have more time to look for a better image, but here is a link that shows what I am referring to.

3 Warning Signs of V-Belt Premature Failure

To ensure that your V-Belts have a longer lifespan, it is important that you look out for the following warning signs of premature belt failure.

blog.slsbearings.com

Likely just the angle of the pic, but the first one looks like there could be an alignment issue as well. Put a straight edge on it if you haven't yet.
edit; Forgot to mention, it looks like there is a bolt missing for the smog pump or whatever is below the alternator.

 

[75gmck25]

I have used the same 15445 Belt with a 12si on my ‘75 350 for many years. The only time I get a short belt squeal is if the battery is low (left lights on, etc.) and I rev the engine up quickly. I assume the alternator starts to charge more to recover the battery and the belt slips a little.

 

[dec322]

When you say you have tried different pulleys, were they used?
Take a look at the depth your belt is sitting at on all the pulleys. It looks to me like the belt is sitting too deep in the one for your alternator. The running surfaces should be straight and the belt should be sitting at or at least very close to the top of the V.
Sorry, didn't have more time to look for a better image, but here is a link that shows what I am referring to.

3 Warning Signs of V-Belt Premature Failure

To ensure that your V-Belts have a longer lifespan, it is important that you look out for the following warning signs of premature belt failure.

blog.slsbearings.com

Likely just the angle of the pic, but the first one looks like there could be an alignment issue as well. Put a straight edge on it if you haven't yet.
edit; Forgot to mention, it looks like there is a bolt missing for the smog pump or whatever is below the alternator.

The pulleys are on rebuilt alternators. I'm on my third alternator. Thank you for the reference as the belt does sit a little lower in the pulley. It's not flush. Maybe this would cause the heat issue on the pulley?

I have used the same 15445 Belt with a 12si on my ‘75 350 for many years. The only time I get a short belt squeal is if the battery is low (left lights on, etc.) and I rev the engine up quickly. I assume the alternator starts to charge more to recover the battery and the belt slips a little.

This is interesting as I left the lights on the other night and had to jump the truck. I'll test the battery and see where its at with the truck off and the truck running.

 

[Randy and Easton]

We are with @Snoots and @Buck69 bigger belt. Here is a pic of E’s setup. Got belts on Amazon which has a Goodyear belt section with free shipping and returns. Due to our custom set up, we ordered several different sizes and sent back the ones we did not use. Very convienient

Randy and E

 

[dec322]

I appreciate all the help. It's been a while since I've had a vehicle worthy of forum fun (1988 mustang gt....15 years ago).
Plot twist: I removed the alternator belt and fired it up. Still have a chirp which goes full squeal in upper RPMS. I removed the belt to the smog (?). Still had the noise. I removed the belt on the non-functioning a/c and it is all quiet again.
I'm still confused about the heat on the belt/pulley of for the alternator. Maybe it's slipping due to being too small. I will order a new belts and I will install a bigger wire from the alternator to the battery. I've seen 6 awg used on the site. I have 4 awg used for the stereo. Can that wire be used in this application?

 

[Snoots]

Yes

 

[fast 99]

Have to respectfully disagree that belt construction is the issue unless width is incorrect. I have installed almost every brand belt out there and with the exception of serpentine belts never had a drive issue like this I could blame on the belt.

On pulleys, what you need to pay attention to is crank and water pump diameters. It's hard to explain. The comparative difference needs to be the same. We are referring to the alt belt only. If the pully sheave diameters are same on crank, they need to be the same on the water pump. If they are different on crank, they need to be different on the water pump. Reason it seems to be alternator pully related is the surface area of that pully is less than the other pulleys in the arrangement. I could be wrong pictures don't show what I need to make that determination.

Pictures below show a drive with different diameters that are matched, if that makes sense.

Don't start making additional changes. Alternator wire size and a small pulley will not cause this problem.

You must be registered for see images attach

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[dec322]

Have to respectfully disagree that belt construction is the issue unless width is incorrect. I have installed almost every brand belt out there and with the exception of serpentine belts never had a drive issue like this I could blame on the belt.

On pulleys, what you need to pay attention to is crank and water pump diameters. It's hard to explain. The comparative difference needs to be the same. We are referring to the alt belt only. If the pully sheave diameters are same on crank, they need to be the same on the water pump. If they are different on crank, they need to be different on the water pump. Reason it seems to be alternator pully related is the surface area of that pully is less than the other pulleys in the arrangement. I could be wrong pictures don't show what I need to make that determination.

Pictures below show a drive with different diameters that are matched, if that makes sense.

Don't start making additional changes. Alternator wire size and a small pulley will not cause this problem.

I did read about the different size crank and water pump diameters causing issues. Thanks for the pics...it does help.

I am changing the wire size because the amps on the old alternator was 66 and the new one is 98. I won't change the pulley size and was talking about changing the belt to sit a little higher in the pulley.

 

[Ricko1966]

I did read about the different size crank and water pump diameters causing issues. Thanks for the pics...it does help.

I am changing the wire size because the amps on the old alternator was 66 and the new one is 98. I won't change the pulley size and was talking about changing the belt to sit a little higher in the pulley.

You do not need to change the wire.even after the squeal is corrected. Stay on task fix the squeals. Maybe the angle of your pics,but looks like an alignment issue. Pay attention to what fastvsays he's very knowledgeable your heat is from the friction of the belt slipping on the pulley, put a penny on your finger rub it on your jeans fast and hard ,it will get hot. The belt slipping across the pulley does the same thing. Quit changing alternators they are not the problem,and everytime you change a part you add a new piece into the equation.