so my sister in laws taurus started discharging the battery while driving making the car die. she put a brand new battery in it thinking it was probably the battery. it done it again today so obviously it wasnt the battery. a guy she knows supposedly tested the alternator by taking the hot wire off the battery while it was running and he said it kept running. i do it today when we get it back to our garage and the car dies which means the alternator wasnt charging. the obvious thing would be rebuilt alternator. however i google this problem and see a lot of different theories on what is wrong. everything from bad wire connection from alt to fuse block, to a possible blown fuse, to bad serp belt and/or pulley on motor. shouldve added that many people said they replaced alternator and light was still on

has anyone had any problems with fords around this year and the charging light coming on? it looks like im going to have to do a lot more checking of parts because i dont want to get another alt and that not fix the problem. damn batter was over 100 dollars.

2006 ford taurus SE 3.0L

This post was edited by JDH on Mar 29 2013 05:46pm

Have the alternator tested. Don't keep running that battery dead.
You can do it yourself with a multimeter. Should be at or close to 14 volts at the back.
Other than that visually check all the cables and the belt. If it's spinning and the car runs alright I doubt it's anything pulley related.
Fuses are also doubtful.

This post was edited by OEM on Mar 29 2013 06:42pm

it was something about a fuse that tells the alternator when to basically turn on and charge. and yes i know its spinning the entire time but im assuming it can somehow bypass storing the charge its making maybe. im not familiar with fords so thats why im asking in case someone knows some kind of obscure thing like that about them.

and im going to use a multimeter tomorrow to see what its doing. its almost like it charges sometimes but then it randomly doesnt charge. i put her old battery back on it and she drove it about 15 miles back to the garage with the charging light coming on but the car ran fine. she shut it off and it started right back up. i wouldve thought with a bad alternator it would kill the battery every time you had the engine running which is what i originally told her. it just sounds like others have had this problem and no one really has a definite answer on what causes it. im hoping its not too much of a headache tomorrow lol

The fact that it's intermittent makes me think even more of the alternator. If a fuse or something was blown it wouldn't work sometimes. Those are either on or off.
Could just be on its way out and it hasn't failed completely. Is there any play in the lead on the back of the alternator? Sometimes they get loose internally and it'll do what you're describing.

Similar thing happen to my Lexus ls430 change the alternator.

Rectifier is bad, need new alternator.

yeah i wouldve expected it to just went out really and not sometimes work alright and other times it takes a shit on the battery. im going to check it out today once i get over there and see what its doing while the car is running and stuff and i can get it checked when i take down to the alternator shop. i just saw a lot of people having this problem and still having the light and stuff after changing alternators and am worried it may be something else.

If you wouldn't have read all that junk, you'd be almost convinced that it's the alternator, yes? Leave other people's opinion out of it, and go with the obvious solution. Sounds like a bad alternator to me, that's the first thing I'd check.


Also, don't ever run a car off the alternator without the battery hooked up. Your car runs on 12 volts, not the 14+ that an alternator will put out. The battery acts as a voltage filter; it takes the 14+v input and outputs the proper 12v.