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Alternator is screaming, but why?

45% is almost halfway around,that should be sufficient--most OEM v belt setups are lucky to have that much belt "wrap"...

I've had several different alternator belts on my 6.2 Suburban and all but one screech like hell after a cold start,until the fast idle solenoid shuts off...
Gates belt was worst,I tried a Dayco "cogged" belt and it was quieter,but still screeched for a short time after a cold start..

Dayco listed a 15/52"thick belt (15480) as "stock" and a 17/32" one as "heavy duty"(17480) and the thicker one was much quieter,but also did not sit flush in the alternator pulley,and eventually it wore the sides off and the top cover flew off it..
The 6.2's v belt setup never was stellar to start with,really..

But any belt will squeal if the alternator is trying to max out,new old,so I'd still look for excessive draw first..
 
Can you take a pic from straight on top to show belt alignment. Are both crank pulleys same diameter? In the current state have you tried tightening the power steering belt?
 
Belts are lined really well, better than my other cars tone honest. Have not touched the PS belt.

image.jpeg
 
Kinda a shitty pic, it's on the lift.

We gave the new battery a little more juice, it's at 13.5v. Also reinstalled the first CS130 alternator since it's clearly not an alternator problem and it's rated at 160 amps. Started it and same results, it bumped up to 13.5v when I revved it. We're going to try removing the started from the circuit after starting it to see if we still have the draw issue.
 
Your belt looks good. I have a bar stock pulley like that on 2 of my trucks. I have jump started a 3 battery semi with one and no problem.
 
Tighten up the power steering belt. See if that works

The crank pulleys look like the power steering one is smaller? Difficult to see on my phone
 
If the alternator is direct to the battery, how will it continue to run if you pull the starter cable? The rest of car feed of battery or off starter?
 
frankin5 said:
If the alternator is direct to the battery, how will it continue to run if you pull the starter cable? The rest of car feed of battery or off starter?
Click to expand...

There is one wire off the starter that feeds the ignition switch, we disconnected that and hooked it up to the battery for the test. Some other accessories get power direct from the battery.

ChrisPerry said:
The pulleys, are they different sizes?
Click to expand...

I haven't measured them but they appear to be different. We put the longer alternator belt back the way it was, around the crank, water pump and alternator. The other belt goes from the crank, around the water pump and then around PS pump.
 
skunked said:
There is one wire off the starter that feeds the ignition switch, we disconnected that and hooked it up to the battery for the test. Some other accessories get power direct from the battery.



I haven't measured them but they appear to be different. We put the longer alternator belt back the way it was, around the crank, water pump and alternator. The other belt goes from the crank, around the water pump and then around PS pump.
Click to expand...
If the crank pulleys are different diameter, the water pump pulleys will have to be different too, or the belts will squeal no matter how tight they are.
 
ChrisPerry said:
If the crank pulleys are different diameter, the water pump pulleys will have to be different too, or the belts will squeal no matter how tight they are.
Click to expand...

ah yes, you're referring to different diameters on one pulley. Yes one of the three on the crank pulley is larger, we're not using that one. It fired right up, quiet as it can be without any squeal once we tightened the PS pump. Not sure why that was causing the squeal being a different belt an all but it's fixed. Now we can roll it out and get back to the FiTech tweaks that need to be done. I knew it was something stupid.
 
skunked said:
ah yes, you're referring to different diameters on one pulley. Yes one of the three on the crank pulley is larger, we're not using that one. It fired right up, quiet as it can be without any squeal once we tightened the PS pump. Not sure why that was causing the squeal being a different belt an all but it's fixed. Now we can roll it out and get back to the FiTech tweaks that need to be done. I knew it was something stupid.
Click to expand...
Ok, glad it was simple. Look forward to seeing a video of that thing out running around
 
Weather didn't cooperate with us so we didn't pull it out of the shop. Tomorrow we'll take it on a cruise.

Thanks for all the help guys :beer:
 
The power steering belt was carrying all the load of the alternator and the water pump until you put the belt back on the crank pulley.
 
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