Need Help Diagnosing Bad Alternator

[djkymar]

yes i did check all my cables adn connections and everything good. The story with is going on for awhile when i had my old battery it happend only when i used my horns at night then my battery died i got new one adn everything was still the sane (dimming at night only) but a couple weeks ago i nocided it dimms when i roll my windows up and even at day time i can see light on my dash dimming a lit bit without headligths on. So i start suspecting my alternator and im probly going to get the one that biju reccomended.

[Dino]

I have driven it more than an hour once, but mostly short 20 minute drives. Yup, the battery tested okay. Just today, I checked my VX--Of course it wouldn't start, but the lights, radio, & windows work after sitting untouched for about 2 weeks. How can I tell if something is draining the power while it's sitting (not in use)?

Try this:
http://vehicross.info/forums/showthread.php?t=11247

[Tone]

Did you DISCONNECT the cables and then reconnect them? I just had an issue like this on my ML and it was the positive post not being clean and tight - lights dimming when running, unable to start. Or dang, take it to a parts store and let them bring the tester out instead of jerking around with it.

[grober02]

Thanks for everyone's advice. I'll try some more thorough testing this weekend. Advanced Auto did use a rolling tester to check the charging system. And, even before that, I removed the battery and had it tested at 2 different places--both said it's fine. It is, however, a 3 year old Wal-mart special...

[djkymar]

grober,
Try go to Autozone and something like that and get brand new battery adn try to start your VX if it wont start then def not a battery.
just my 2 cents

[Cobrajet]

It is, however, a 3 year old Wal-mart special...

Oh, NO!!! I fought battery issues like yours for the whole three years I had one of those in my Mustang. I didn't drive it too often and it would rarely start without a jump pack. I was trying to off-load the Mustang to my ex-brother-in-law, so I didn't want to buy another new battery. However, after three years I finally relented and bought a Sears Diehard. Now she cranks right up every time and the lights don't dim with the brakes. I wouldn't recommend one of those batteries to anybody. I'd go Diehard, Optima, (or original Motorcraft in my Mustang.)