Battery light on when cranking
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5th Wheeling
Joined: Jan 2017
Posts: 32
Likes: 0
From: Ford City, PA
Battery light on when cranking
When I go to start my truck it cranks for a few seconds and my battery light comes on in my dash. I have two new batteries and my scan gage never goes down below 47v for my ficm. Sooo if it's not the ficm or batteries then what could it be? Or am I just worrying about nothing
Laughing Gas
Joined: Oct 2013
Posts: 817
Likes: 6
Exactly, and they won't get a charge at the low RPM during cranking. As soon as the engine starts and runs at normal idle RPM or higher, it should charge the batteries fine and the light should be off.
Lead Driver
Joined: May 2014
Posts: 6,545
Likes: 13
From: Virginia Beach VA
I would also say that the PCM would need to command something as well. With glow plugs still running up to 120 seconds after the motor starts, they eat a lot of amperage. Withing a couple minutes, you should see 13.5v or more from the alternator.
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