What is the state of charge of the battery? The specific gravity of each cell is a measure of that. If they are low, put it on charger overnight and test again. If any are still too low you have a bad cell there. If the battery is greatly undercharged, the alternator cannot be depended on to do the job.
How do you test the specific gravity of each cell if it’s a sealed battery?
Tester
If it doesn’t have removeable caps, you have to rely on electronic measurements, since the SG cannot be measured. You showed a printout of one of those electronic battery condition tester’s measurements here a few days ago.
Do you think the battery’s condition might be part of the OP’s problem with the 2 new alternators?
One way to find out is, ask the OP if the replacement alternators came with this warning?
And if they did, did they heed that warning?
Tester
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The battery is new.
But is it fully charged? Did you use a battery charger?
If you’re using the alternator to charge a partially charged battery, you risk burning up the alternator by making it work to hard.
I presume you have a DC volt meter. What voltage do you measure at the battery before first start of the day? Next, what voltage do you measure immediately after starting and idling the engine?
I am beginning to wonder if the noise you are hearing is caused by something else but the alternator. I can not imagine an alternator “squealing”. At most it might make a growling noise. I assume all the alternators you purchased came with a pulley installed.
In your original post you indicated that you had voltage and starting problems with the old alternator. Are you still having this problem after installing the new one?
Yes, it is the same issue. The voltage is low and it squeals, no grinding. I think something is causing the alternator to work way to hard. After driving the car with the third alternator it worked fine, low 14 volts. The next day I started driving and after I used my windows and radio it screeched again and now is back down to 12ish volts. I think it is either a resistance somewhere in the electrical like, such as a bad ground or damaged wire. The other thing is possibly the battery.
I realize this an older thread, and its probably no longer an issue. But I did have a thought on it. Did you check to see your auto belt tensioner was still working properly. I personally have had one on which the spring was weakening, and by extension causing issues with pulley squeal. Just an idea.
It was the alternator. We sold it to friends who replaced it one more time with a different alternator brand. The car has run fine ever since.