Alternator issues

I just bought my '93 B2600i and a new battery, old one was completely dead and 10 years old. My truck died a couple days ago and sure enough the battery was dead... today I took my alternator in to Autozone and got it tested, said it passed all of their tests. So now I'm not sure what the problem could be. Replaced battery terminals today and noticed there's a red wire, probably about 6 gauge that runs from the passenger side firewall to over by the battery and has a metal loop on the end like it would be attached to the terminal or somewhere else. Anyways, the wire is not connected and I don't think it was when I bought the truck either.

Any ideas what my problem could be?

Zac

I'd bet the alternator is bad, I had a new one tested at Auto Zone that was over charging that they tested and said was good, same thing for the old one that would kill the battery over night, what has gone bad is the internal regulator. With the engine off the bad regulator puts a short on the battery. With the engine running check the voltage across the battery, a good alternator should read 13.5-14v.

I checked the voltage yesterday, it was the same as when the car wasn't running.. about 12.8 if I remember right.

Anything else I should check before I pay and get a new alternator?

Nothing else to check, if the voltage is the same with the engine running and when its off the alternator is not working and its also draining your battery when its off, its the regulator in the unit that's gone bad. Be sure and check the output of the new unit at the battery, the voltage should be around 13.8-14.2 if its much higher say 14.8-15+ take it back and get another it will cook your battery.

Thanks, I was just making sure it couldn't be any sort of a wiring issue, like the unhooked red wire I mentioned. I was hoping maybe that would be the alternator wire and just needs to be hooked up, wishful thinking huh?

In that case, I think I'll head out to the pick and pull and see if I can't get me an alternator and radiator.

Cool well it looks like I found both an alternator and radiator from a friend of a friend. Any tips on how to get the new belt on there? Looks like I might have to remove the fan and will definitely have to temporarily remove the other belt on there (not sure what it's called).

The belt should slip over the fan, you don't have to take the fan off, the other belt(s) are ac and power steering, the other belts don't have to be removed as the alt. belt is nearest the front as you will see when you get the new alt. installed.

On my engine the alternator belt is closest to the engine, and then the power steering belt. No A/C on my truck. Unless something is hooked up wrong... I'll take a picture tomorrow morning.

My truck is an 86 and the ps belt is first (closest to the engine) then the ac and last the alt belt. The alt bracket will determine the belt position on your truck, but all the belts are removable without removing the fan, once you've loosened the belt just slip it off the pulleys and work it over the fan, pretty easy actually

That explains it, mine is a 93. Which means yours has the Mitsubishi 2.6 and mine has the Mazda 2.6, I believe. Sounds like I'll just have to loosen the PS belt somehow to temporarily take it off, then I'll be able to get the alternator belt on.