Battery Not Charging

az'03Silverado · April 7, 2011

Hey Everybody,

A couple of months ago I installed a new alternator because the old voltage regulator was shot causing a fault in my airbag system. It's been working fine. But, last night while driving home from work on the freeway, the battery light came on for about 3 seconds and a message "Battery Not Charging" read on the DIC. This happened about 3 times while cruising. Then twice this morning. I checked the battery cables and got about half a turn on the negative so I'm hoping that fixed it. I'll find out tonight on the way home.

Is there anything else it could be? Bad battery? The truck's computer? Bad new alternator? Any thoughts would be great. Thanks.

pm26 · April 7, 2011

Get a multimeter, set to at least 20 DC voltage range, and check the battery voltage with the engine off. It should be around 12.5 to 12.7 Volts for a fully charged good battery. Then start the engine and check the voltage at the battery terminals with the engine idling and accessories off. You should be between 13.5 Volts - 14.5 Volts. If the voltage with engine running is not higher than the static battery voltage, the alternator will not charge the battery.

You can also take the truck to Auto Zone and they will check this for you for free. Auto electric shops that rebuild alternators and starters also do full charging system tests with the alternator in the car. Checking the alternator for full current output requires a fairly expensive meter with a resistor bank. The local shop around here will typically do a test like this for $ 10.

az'03Silverado · April 7, 2011

Driving home last night the light would come on for about 5 seconds then go off. This repeated about 10 times on a 25 minute drive. The voltage stayed above 14 the whole time even when the light was on. Could this just be an indication problem? It seems the alternator is still working right even when the batt light is on.

dewfpo · April 7, 2011

When the dash light came on could you tell if the headlights dimmed at the same time?

DEWFPO

az'03Silverado · April 7, 2011

No, everything stays the same. The light only comes on for 4-5 seconds then goes out. Does anybody know what each of the 4 wires in the alternator plug does? I'm thinking that the signal that the alternator gives the computer that it's working is getting cut off momentarily.

I have noticed that when I first start my truck up in the morning, the headlights and interior lights flicker very slightly. Then they seem to get more solid after a minute or two.

I borrowed my boss' Power Probe today and will check the voltage tonight on the way home from work as I drive.