GregHamilton

My Silverado 2000 Z71 low battery indicator came on the other day just before I stopped at the store. When I tried to start it, it just clicked. The sticker on the battery shows it was a 2005 battery, so I paid a $100 for a new battery. I noticed right away that although my truck usually runs at 14 volts per my battery gauge, the new one was only running at 12 volts and I was already getting the idiot light again saying the battery was low. It ran for a couple of days as I was hoping the alternator would charge it up. I thought batteries were 12 volts, so I'm kind of unclear as to how mine always ran at 14 volts anyway. Anyway, even though I drove it to work and back, it never got any higher than 12 volts. I noticed my gauge lights getting dimmer on the way home this morning as I work nightshift. About a mile away from home, all my gauges shut off except for my oil pressure gauge (probably an electricity saving technique) and then my truck started acting like it was in 4-wheel drive (making the same noises, getting squirrelly going around turns, etc.). I'm wondering if there's not enough voltage if my truck reverts to 4-wheel drive. Even though all my gauges except for my oil pressure gauge went dead (even my radio went out), I did note that where my 4 buttons are for all-wheel drive, 2-wheel drive, 4-wheel high, and 4-wheel low, it did show 2-wheel drive even though it was acting like it was in 4-wheel high. Anyone have any ideas? Thanks.

Thumper_ehhhhh

Sounds like your alternator is shot. Im not sure which one you have on it. On the back of my old cars alternator it had a wire going to it seperate from the harness. Put a meter on there positive side and ground the other lead to something metal. When you have it at idle check it and have someone rev it up to see if the volts go up if they dont or drop below 10volts its shot. Time for a new alternator. I just had to do the one on my wifes car a few months back.

MDTAHOE

The alternator is dead. Your gauge used to read around 14 because the alternator charges 13.5-14.5. The light should really be called a alternator light not a battery light. 98% of the time that light comes on it is the alternator.

GregHamilton

Thanks for both your help. Sounds like I may have just wasted a hundred bucks....,but if the battery was really 5 years old, maybe it was time. Any more advice on exactly how to check the alternator (i.e. exactly where to put my voltmeter leads, etc.)? Also, you used to be able to get rebuilt alternators. Is that the way to go or should I buy new? Should I try to go back with stock (probably Delco), or something different. I have one of those serpentine belts too. Probably a good time to change that if it is showing any wear. Thanks.

MDTAHOE

Well you battery gauge is doing the same thing as your meter. When testing a alternator amperage is more important than voltage, you can still have normal voltage (not in your case) and little or no amperage. You are safe in replacing the alternator without doing any more testing. Almost all the alternators sold in parts stores are remanufactured. You can go with one from any parts store, the more warrenty the better.

GregHamilton

Okay, thanks. I'll change the alternator and see what happens.

GregHamilton

I replaced the alternator and the problem was resolved. It started right up and was immediately showing 14 volts on my gauge. Thanks.

Thumper_ehhhhh

Glad it worked out for you.

GregHamilton

Thanks.

coppola7

Well I have the opposite problem. Recently replaced the battery (it was leaking). All was well until recently the voltage gauge is reading greater than 19 volts, red lined. The truck is running fine. I don't want to overcharge and destroy a new battery. Is this a voltage regulator problem, a bad gauge or something else. How can I check it. Thanks.