Alternator/Electrical issues!

[Tall]

Hey all, I have a weird problem.

I have a 1990 C-1500 with a 350 Auto tranny.

I was driving home Saturday and all the sudden my voltage gage dropped to 9v, the truck started sputtering and the radio cut off. I than pulled over in a parking lot and tested the voltage on my alternator. It was at 14v(truck was running) I checked the voltage at my fuse block it was 9v. I tested voltage at the distribution block under the hood it was at 14v(truck was running).

Now if this wasn’t confusing enough, after I shut the truck off and was under the hood. I heard a buzzing noise. It was from the alternator, with the truck off and keys out! So I replaced the alternator, only to find out the new one does the same buzzing sound with the keys off!

Any idea on what could be causing this? Oh, and with the voltage at 9 the truck sputters and dies a lot. I am confused. I hate electrical problems!

[2000CAYukon]

Might be a good idea to get the new alternator bench tested at the parts store where you bought it (most stores will do this).

It almost sounds like something is really draining the battery and the alternator is trying to keep up.

What shape is the battery in (how old is it)? I would also check both ends of both battery cable for good clean connections.

//2000CAYukon