Battery light comes on and off randomly

Tiny
DREWBIDOO
  • MEMBER
  • 2007 FORD MUSTANG
  • 4.0L
  • V6
  • 2WD
  • AUTOMATIC
  • 174,000 MILES
My car has a battery that’s only about a year old. There is a little or corrosion on the terminal but I cleaned off as best I can and I can’t remove the terminal because it’s hard to get off. I recently replaced the belt because it was cracked. The light comes on randomly and sometimes doesn’t come on at all while driving. For example I went about 95 and got no warning light using the radio and everything. I left where I was and the light came in after about 15 miles and went off for another 10 and then proceeded to come on and off every 10-15 minutes. I’m not sure if it’s a wiring issue or the alternator. I had the battery tested with the car off and the charge is good. Had the battery tested car on and same thing. I had the alt tested and it’s read 14.3v so it passed. I’m really not sure what it is but I don’t want to spend money to replace the alt just for this issue to continue. Does anyone have any better guesses?
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Tuesday, November 23rd, 2021 AT 1:06 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

It does sound like either a connection issue or the alternator is starting to fail. What I suggest is this. The alternator output needs to be checked when the battery light is on. It won't even require you to turn the engine off.

When the light comes on, follow the directions in the following link. It explains how to test the alternator using a multimeter or a voltmeter.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

The link suggests testing with the engine both off and on. If you let me know what voltage is showing while it's running, I can tell if it is charging.

Try this and let me know the results. Also, please feel free to let me know if you have other questions.

Take care,

Joe
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Tuesday, November 23rd, 2021 AT 8:35 PM

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