What the hell did I do??? - low voltage

Ok guys,

So in trying to diagnose my transfer case issues I disconnected my battery last week...problem is I fell asleep for 3 hours instead of reconnecting it after an hour. a few days later my voltage guage started fluctating and odometer started flickering. Did I cause this?? I tried charging the battery for about twenty minutes with some portable jump start unit I got for Christmas a couple years back. Am I looking at a new alternator, battery or should I go get charged for real some place. Thanks!!!

BTW - I do get the whirring sound, which sounds very much like alternator problems, I know cuz I had 4 replaced including the original one.

Here is the easiest thing to do if you want to figure out if it is your alternator. Turn on your blazer, stick a multimeter on your battery terminals. It should read ~14v on the multimeter. If it starts fluctuating, you have a bad alternator like you suspect. If it doesn't proceed on.

Turn off your car then touch the battery leads again. Should read ~12v. If you think it is going bad, take it in for testing.

edit: my lights flickered b4 my alternator went out last summer.

Just so that you know, your battery can be disconected for weeks and even months at a time without causing any damage.

It's just a coincidence that it happened at the same time.

Here is the easiest thing to do if you want to figure out if it is your alternator. Turn on your blazer, stick a multimeter on your battery terminals. It should read ~14v on the multimeter. If it starts fluctuating, you have a bad alternator like you suspect. If it doesn't proceed on.

Turn off your car then touch the battery leads again. Should read ~12v. If you think it is going bad, take it in for testing.

edit: my lights flickered b4 my alternator went out last summer.


My buddy told me when mine was going that if the car is running and i disconect one of the battery leads, If the car shuts of the alt is bad. If it keeps running the alt is fine. Im not sure how safe this is on the car and all of its compents. I didnt try it, turns out it was my battery any way

Ok Guys...I know what the hell I did...

I didn't go buy a $4.99 terminal wrench so I could make sure the connection was tight again. I tightened them and everything is A-OK. I just left Auto Zone and everything is great, no gauge fluctuation.

Sorry for the trouble.