Alternator or Battery? Can't afford ammo for the "Parts Cannon"

[y0diggity]

Here's what's going on -
Since it's started getting cold overnight, my truck will start then die out after a few minutes. When I try to restart it, it makes the "battery dead click sound". After sitting a few minutes, it will start again but then the same thing will happen.
I can jump it and it runs great while attached to the other car, but disconnect it and it will die again in a little bit.
I've tried driving it and it will go a little ways (maybe a few blocks) and then it won't go above about 1500RPM and then it will die again.
The alternator makes a buzzing humming noise and a noticeable vibration can be felt when I put my hand on it. -- That's assuming I'm putting my hand on the right thing. I think it's the alternator - top right of the engine in the "belt array". I would say it almost feels like a spun bearing in the alternator. the reason I think that's the alternator is because all of the other devices in that area seem to have "non-alternator-ish" stuff hanging off of them.
I can fix either the alternator or the battery, but I'd rather not replace them both if I can avoid it. Times are incredibly tight right now and Christmas is already looking slim at the 'diggity house.
Please help me with a course of action.

Forgot to add that it's a '95 2 door.

 

[Ed Blown Vert]

It sounds like the alternator. The battery is used the start the engine, then the alternator should keep it running.

 

[y0diggity]

Ok. that's also what I was thinking. I heard that parts stores will test them for free, but I haven't called them yet to verify.

 

[y0diggity]

I've also heard that if I have the engine running and I disconnect the battery cable, it should stay running from the alternator, is that true? I've heard that if I do that and the truck dies then the alternator needs replaced. If so, which cable should I disconnect? Please confirm if you know the answer. This really sucks; the timing on these things is always terrible, isn't it?

 

[Ed Blown Vert]

Yes that should work. Your lights should also get brighter. After you start the engine.

 

[TahoeGoBoom]

My alternators fine, but it i disconnect the battery it still shuts off. so i wouldnt use that as a means of testing. but from what your saying it sounds like the alternator.

 

[95TwinTT]

What voltage reading do you have when you turn the ignition on B-4 starting, and what reading do you have after the engine is running?

 

[y0diggity]

You mean on the battery itself? I dono, I can check it when I get home. What should I look for?

 

[95TwinTT]

The volt gauge in the dash. It should read 12 volts B-4 you start the engine and after it's running it should read 14 volts.

 

[y0diggity]

I'll probably have to use a meter. I don't think I have a volt guage. I might, I guess I've really never looked. I've only had the truck for a few weeks...

 

[y0diggity]

Thanks folks. It was the alternator. Got it replaced and it's back to normal. I had the toughest time figuring out the belt tensioner, but once I got the hang of it, the task became simple.
BTW, I do in fact have a voltage guage on my dash. I never really looked before so I had no idea. I might actually pay closer attention to it from now on.

 

[Ed Blown Vert]

Sweet