Battery Light on Startup
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Battery Light on Startup
Hey guys,
Long story short: I bought my 2003 F-250 super duty 6.0 used back in January. It had one Ford OEM battery and one Walmart special. I had them tested and they were both completely flat. Replaced the set of batteries the next day. Since then, upon cranking the truck, the battery indicator will be illuminated while the truck is running. It will stay on for a length of time that varies based on the day. It will eventually turn off after driving a while, but will come back on if I kill the truck and crank it again (like when running to a store).
The batteries have been tested 4 times and test just fine. No problems with the batteries. The OBD 2 computer/monitor I have installed reads a voltage of around 13 when the truck is running. I have no idea what to do to solve this problem. It isn't a major issue as the truck always cranks fine and the batteries are not damaged or anything, it is more of a annoying thing. It bugs the crap out of me.
Any ideas what the cause could be?
Long story short: I bought my 2003 F-250 super duty 6.0 used back in January. It had one Ford OEM battery and one Walmart special. I had them tested and they were both completely flat. Replaced the set of batteries the next day. Since then, upon cranking the truck, the battery indicator will be illuminated while the truck is running. It will stay on for a length of time that varies based on the day. It will eventually turn off after driving a while, but will come back on if I kill the truck and crank it again (like when running to a store).
The batteries have been tested 4 times and test just fine. No problems with the batteries. The OBD 2 computer/monitor I have installed reads a voltage of around 13 when the truck is running. I have no idea what to do to solve this problem. It isn't a major issue as the truck always cranks fine and the batteries are not damaged or anything, it is more of a annoying thing. It bugs the crap out of me.
Any ideas what the cause could be?
Token Redneck
Joined: Jun 2007
Posts: 9,337
Likes: 346
From: Breckenridge, TX
It's not an annoying thing, you've probably killed the FICM; the power supplies in it are sensitive to voltage drops and will actually burn out the board they're soldered too if you run them at too low a voltage for too long.
Your alternator isn't just dying, it's too small. The glowplug draw during the first 120 seconds of a cold start will draw significantly more than the output of a stock alternator, so depending on how bad of shape the alternator is in it might not be able to put out enough charging current without the voltage dropping low enough to set the light. The hot restart light is because the hot output of the stock alternator isn't enough to run the body electric with the HVAC on max and charge both batteries without dropping. Bare minimum to run the 6.0 with basically any accessories is a 140A alt with a 58mm pulley.
https://www.ford-trucks.com/forums/1...lternator.html
https://www.ford-trucks.com/forums/1...tery-life.html
https://www.ford-trucks.com/forums/1...lternator.html
What's "normal" will depend on the alternator's voltage regulator setpoint and it's output capacity. 14.6 is higher than you'll see with a stock unit, and it shouldn't stay there all the time. Running an LN230 it charges at it's 14.2V setpoint then drops to 13.5-13.7V after the battery charging draw falls off.
Your alternator isn't just dying, it's too small. The glowplug draw during the first 120 seconds of a cold start will draw significantly more than the output of a stock alternator, so depending on how bad of shape the alternator is in it might not be able to put out enough charging current without the voltage dropping low enough to set the light. The hot restart light is because the hot output of the stock alternator isn't enough to run the body electric with the HVAC on max and charge both batteries without dropping. Bare minimum to run the 6.0 with basically any accessories is a 140A alt with a 58mm pulley.
https://www.ford-trucks.com/forums/1...lternator.html
https://www.ford-trucks.com/forums/1...tery-life.html
https://www.ford-trucks.com/forums/1...lternator.html
What's "normal" will depend on the alternator's voltage regulator setpoint and it's output capacity. 14.6 is higher than you'll see with a stock unit, and it shouldn't stay there all the time. Running an LN230 it charges at it's 14.2V setpoint then drops to 13.5-13.7V after the battery charging draw falls off.
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