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Battery Light On - New Alternator, New Battery

grn03exp

Member
Joined
February 22, 2007
Messages
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City, State
Lake Orion, Michigan
Year, Model & Trim Level
2003 XLS 4x4
2003 Explorer XLS 4.0L/Auto, 73xxx Miles

The Explorer is my wifes car, so my original failure information is from her perspective:

For the last month the battery light would come on randomly about once a week, usually for less then an hour. Last friday night the battery light came on and then a few minutes later the radio (Aftermarket Pioneer) started turning off then on repeatedly light the power was being cut. The interior lights started dimming and thats when she noticed the charge gauge was almost all the way down to the bottom. As she pulled in the parking lot, the truck started sputtering, so she shut it off. After that it wouldnt start, it would just click like the battery was dead. After jumping it, it ran fine until the jumper cables were removed, then the charge gauge started dropping.

Today i popped in a reman alternator and when it started within 10 seconds the charge gauge started dropping. Took the cover off the battery (Factory Motorcraft) and looked in the sight glass and saw red. Went to walmart and bought the recommended battery (850CCA/1000CA). Popped it in and now the truck runs and drives normally (tested it on the road for an hour), but the battery light remains on. Not really sure why its still on, cause most of the charging system has been replaced. Checked ALL of the fuses (Under the hood, Under the dash) and there are no blown fuses.

Does anyone know why this light is still on?
 



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have it checked out on a meter or see if it throws a code. advanced auto does both for free.
 












Check the voltages with a test meter. You should get 12.8 volts off, 14.3volts running, anything else report back.

I have bought bad reman alternators before, or some have only lasted a month or two. I'd buy new if the price was right, less problems in the long run.
 






check all the connections around the alternator. Sounds stupid, but i have a 94 toreass and some little clip was loose and the motor would rock and throw the battery light on.

good luck
 






Also make sure a fuse didn't get popped while the alternator swap was going on.

Had a friend with a mustang that swapped 3 alternators before finding out it was a bad fuse because someone hadn't disconnected the battery before swapping the alternator.
 






My multimeter is at a friends house, so im gonna grab it when im there for thanksgiving. As soon as my wife gets home this after noon ill recheck all the fuses again, and check all the connections at the alternator and battery.

Is there any chance this might be a persistent MIL due to the previous failure of the battery and alternator?
 












Well surprise surprise, the truck died again. My wife was driving it on black friday and it did the same thing it did before. Took the alternator to the shop that rebuilt it, turns out the reg was bad and the alt was only putting out 9.8v at < 50 amps. He installed a new regulator on the rebuild and load tested it on the bench for 45 min and it sustained 126 amps at 14.2V. So ill be picking it up and installing it tomorrow along with the second new battery. Assuming all goes well the truck should be fine tomorrow.


Alternator guy says that the old original factory battery it what probably fried the first alt, and the first reman, due to a hard short between two cells.
 












Fixed!

I finally got a chance to pop the second reman and the new battery in. Everything worked flawlessly, no battery light, strong charge gauge, no flickering or dimming. After talking again to the alt guy, it seems that the first battery had a short between two cells which had been slowly killing my factory alt for a while now. Then i put the reman in with the old battery and the short in the battery fried the regulator. So word to the wise, if your alternator dies, have your battery tested before you put the new alternator in.
 






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