View Full Version : Chevy truck guys!!! Battery Light Staying On?????

01-09-2008, 11:55 PM
So my truck is an 03 2500hd duramax, And for the past week my Battery light has been on so today I went out to buy two new battery's 800c.c.a. (because I looked at the Eyes, on the battery and one was black and the other one dark yellow, but I know that is only showing one cell of power not the whole battery) so after seeing that, yeah I sure thought it was the battery. So put them in and all and WTF the light is still ON.

Maybe ALT. but it cant be because even when I turn the Truck off the light stays on.

I looked into it alittle bit and other guys have the same problem and no body knows what it is. Anybody else have this or heard something about it?


01-10-2008, 02:23 AM
Isolation diode in the alternator may be bad. It will kill the batteries and with new batteries, it might finish off the alternator completely.

01-10-2008, 07:18 PM
just unhook the battery ha! ha! with todays vehicles and there computers you should be able to go by a autozone and let them check codes. if you dont have autozones then check your local mech. heck my 02 dodge lets me know i have a light out.

01-10-2008, 07:59 PM
Thanks, I've work in the auto field and the autozone computer is not gonna tell you anything but Codes of "check engine soon" and thats all.

My next step is to check out the ALT. maybe. Like Gravley says, b/c yeah now I remeber about the diode acting as a one way check valve for power. And autozone can Test out my Alt and Diode on there ALT/Starter machine.

01-11-2008, 12:07 AM
Have you checked voltage at the battery? With it running at a high idle? a very common mistake to just replace batteries, but they probably were due on a '03 if they are original. let us know what you find.

01-11-2008, 01:12 AM
Well Yes I did already replaced the batterys and the lights still on, My voltage is at 14.3-14.6 at Idle on both. So I talked with some of my higher working tech buddys and they said its the Diode in the Alt. So im gonna change it this week and let u guys know.