Alternator

Got my stock M1009, 86'. When I bought it a friend said the alternator on the right sounds like it had a bearing going out and the squeak got louder and louder. Sqeak has stoped and now every three days the battery is weak to dead. Is this the possible cause? Does it take a regular alternator or will I have to search for the 24V one? THanks for all the help I have been getting from here.

Not sure about the relationship of the squeak to the weak battery. But your alternator is a 100 amp mil spec 12v alternator and an alternator test is a simple thing to do or have done. (I presume you have two.) They are expensive to replace new (about 200 bucks) but there's really nothing exotic about them, other than they are stout mothers. I have had great success getting them rebuilt at a very reasonable price here in Northern California. I'd try the rebuild route first if testing warrants it.

What is it I need to tell an alternator shop that is doing the rebuilding? Isn't there something special they should be made aware of? I thought it was an isolated ground but I called one guy and he had no idea what I was talking about.

Nothing special. They're just really ruggedly built 12v/100 amp units. Also nothing exotic about the isolated ground. It just means you ground them to the frame via a heavy gauge wire from a terminal on the back of the unit rather than by the contact of their housing to the vehicle. No big deal at all. I'm a bit concerned an alternator repair shop doesn't know that, but I can't imagine they can't figure it out with just one look at the unit.

Bumping this thread because today at the barbershop my truck died. It was the battery(es). I called a friend whose an electrician and he came over and read that one alt. was pulling 20 volts and one was pulling 12. One of them is recharing the the other battery, but one of them is not. I've had some belt noise, but I thought I just needed new belts...

My questions are:
Am I suppose to have 2x 12v alts.?
If one is going bad, would one be pulling 20v to make up for the other?
I know I need new belts, would that be a factor in all of this?

Sorry for the questions and stupidity, but I'm a little dumbfounded...

Here is what I found on mine. It was the red fuse at the bottom of the fuse box that was bad. Replaced it and bam works awesome. If your GEN 2 is not working and the Volt meter is not working, check the fuse. Now I am getting chatter under the dash and no start so I am about to replace the starter relay.

Checked my fuse. It's good. Volt meter works. I'm going to replace the belts, and charge up the dead battery. If that doesn't work I will take off the bad alt and have it tested.

Yes, you are suppose to have 2x12v alternators. 20 volts seems pretty low for that one. it should be up around 26v if i remember correctly from the TM. This alternator looks like it is pushing more because it is the one charging both the front and rear battery. Might as well get new belts while you are in the process of this. But it sounds to me like your Gen2 alternator is goin bad. Hope this helps.

the combined total voltage should be up around 28, as good alts usually put out 14 or more. Dont forget if it's the drivers side alt you can run a 100amp alt available at your favorite parts store, for about 100.00, the application is listed within this site or if you cant find it post back here and i'm sure anyone can give you a part number to look for

BTW, I guess it doesn't matter which one is bad, put the good one with isolated ground on the passenger side and still save 100.00!

Took off one of the alts, had it tested, FAIL. Just got it rebuilt and putting it back on tonight.

For the 109A, its available for k30 pickups, with the 6.2 diesel. Also the Cadillac commercial chassis from the same era had 100A's, but be weary about the mounting brackets, one has two feet at the bottom bracket and one has one big foot, just get the right one.