Battery

I have a 96 GMC sonma and the battery will not build up enough to keep truck running.This battery is only about 1 year old one thing i notice is battery guage hand will drop to 0 after battery has been charged & then truck will began to try & shut off could it be the alternator or could it be a bad battery. Thanks for your help

 

Sure, it could be a problem with your charging system (alternator/regulator, worn or loose belt etc.) a battery that is shorting out internally, and it also could even be poor,coroded or loose cable connections. A one year old battery should still have a good pro-rated warranty left on it if that is the problem. Did you have that checked out from where you bought it? Have you performed a voltage check yet? What checks have you made so far? With the engine running you should be getting about 13.5 Volts out of the alternator for instance. What about the cable connections? Tight and clean?

 

Question. When you say "the battery guage hand will drop to 0 after battery has been charged". Do you mean there is a gauge in the GMC and it drops to 0 after the fully charged battery is put in and is started? Is this guage a voltmeter or an ampmeter? How long does it take to get to 0?

Thanks

 

this would be the dash amp guage only takes about 10 to 15 min. maybe less & this is with lighs on. Thanks for your help

 

When a vehicle is started it drops the voltage of the battery and the regulator reads that and sends field current to the AC generator which then has output. The ampmeter measures this out put and that is what you see on the ampmeter.
During starting the car there should only be the surface charge taken off the battery so it should be full charge again fast.
10 to 15 minutes seems too long for the battery to recover but I could be wrong here. Depends how hard the vehicle was to start. After the battery has recovered voltage then the AC generator stops output to the battery and just supplys the vehicle loads. So at that point the ampmeter should read zero. The loads are being looked after by the generator.
Hmmm? At this point I believe is where you said that the vehicle starts to die.
It that right?

 

Are you sure that your guage is in fact an ampere guage? I think most GM products went to factory installed voltage guages long before 1996 or is this an aftermarket guage in the truck? If not aftermarket then you might still want to consider my earlier suggestions in regards to checking cable connections, belt, battery load testing, and charging system output voltage against the expected 13.5V.

 

IIRC a quick check of an alternator is to see if a metal object (like a screwdriver blade) is attracted to the back center of the alternator when the engine is running. If it's not attracted, the alternator isn't making any juice.

If you put a fully charged battery in and the gauge (I'll bet its a voltmeter if stock) reads ok, then starts to drop and as it gets lower the engine starts to cutout......your alternator isn't working for some reason.

Per the manual...
"When your engine is not
running, but the ignition is
on (in RUN), this gage
shows your battery’s state of
charge in DC volts.
When the engine is running, the gage shows the
condition of the charging system. Readings between the
low and high warning zones indicate the normal
operating range.
Readings in the low warning zone may occur when a
large number of electrical accessories are operating in
the vehicle and the engine is left at an idle for an
extended period. This condition is normal since the
charging system is not able to provide full power at
engine idle. As engine speeds are increased, this
condition should correct itself as higher engine speeds
allow the charging system to create maximum power"

User manual available here...http://www.extendedgmwarranty.com/ow...GMC-Sonoma.pdf