Battery light turning on

2008 FORD F-350
108,500 MILES
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DAVID CALLAHAN2
  • MEMBER
  • 1 POST
I had a bad alternator and replaced it. When the change was done, started truck and battery light came on when I turned on the lights. Shut down the engine, checked connections and restarted the truck. Anytime I run something on, the battery light comes on and stays on until I shut the truck off and restart.
Mar 6, 2022 at 1:04 PM
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SQM
  • ✓ASE Certified Mechanic
  • 6,383 POSTS
  • ASE Certified Mechanic
Hello,

It is possible that the voltage regulator in the new alternator is not functioning properly and is not producing the correct amount when you have more load.
Test the alternator output to the battery with the engine at idle, both with and without the lights.
If there is fluctuation of the output, then the regulator is faulty.

Here is a helpful video and guide on how to test the alternator:

https://youtu.be/Z-p4dMJUpUw

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

I have attached the alternator specifications below.

Please let me know if you have any questions.
Thank you.
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Mar 7, 2022 at 9:28 AM
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