When I was working on my truck recently I had to turn the key on so I could put the truck in neutral and when I was done the battery was dead. I charged it and test drove it and the battery warning came on. I charged the battery more the next day but the warning came on again. I took it to Autozone to be tested and the battery tested bad but the charging system tested ok. I replaced the battery and everything tested fine. I drove out of the parking lot and the battery warning came on again. I went back and everything tested ok again. It’s been a couple weeks since then and it’s working fine except a few times the warning has come on. I have a cell phone charger plugged into the cigarette lighter that displays voltage so I’m keeping it on in the hopes of seeing what the voltage is when the warning comes on. I got the warning the other day but when I looked it was reading 14.4 volts. The battery symbol stays lit until I restart the vehicle. I’ve tried wiggling the alternator wiring harness but that didn’t trigger the warning or make the voltage change. One day it was reading 13.3 for 30 minutes or so but the rest of the time it’s between 14.4 and 14.2 if everything is turned on. I’m wondering if it could be the internal regulator. I don’t know if it is dropping the voltage just for a second and the warning just stays lit or if it is some malfunction with the warning light. Does anyone have any ideas? Thanks Ken

 

Try thoroughly cleaning the battery terminals and cable ends and all connections to it and to the power distribution box take off all the nuts to the attached cables and clean under them. I had this problem a couple times and it was always battery cable connections. I had to replace the positive cable end completely on mine. It could also be a wiring issue to the regulator part of the alternator or internal intermittent issue but I would try the cables first.

 

I had similar problems just before and after a battery change. Unplugging the Battery Management System on the negative battery cable cleared everything up. Might be worth a try.

 

that battery management system tells the regulator if its allowed to charged or not... Unplug it !! .... also when you CHARGE the battery, you need to put the NEGATIVE clamp on the engine block so it charges THRU the ground cable and BMS unit.... or it will not realize you charged the battery... UNPLUG IT !

 

I went through an intermittent battery light on my 2013 with a 5.0. Turns out it was the fuel pump fuse getting hot and making intermittent contact. One day the fuel pump fuse blew which lead me to look at what could cause it to fail.

I have a post covering my trouble shooting with the final fix. The local parts store just happen to have a fuel pump relocation kit in stock which also uses a larger 20amp block style fuse and not the little 20amp one from the factory.

Not saying it's your problem but worth looking into.

 

Well it turns out it looks like it was the Battery Management System. It’s been a few weeks since I did the BMS reset and it seems to be working normally now.