2002 gmc sonoma dont charge

my sonoma woont hold a charge i have already had alternator tested was told its as good as any they would give me off their shelf we checked all connections every wire to


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Moving to electrical forum.

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''Life's tough, Pilgrim, and it's even tougher if you're stupid.''---John Wayne

Midnight Sun Street Rod Association

More likly than not if the alternator is charging properly, the battery is going away. the battery test is to pull a heavy discharge then measure the specific gravity of the electrolyte and how long it takes to recover a charge.

The risk is that if the battery is internally shorting cell to cell it could develop enough of a ground path that the alternator commits suicide trying to match the discharge rate (it will rise to the occasion till it burns out). The sooner you fix this the less likely you'll be buying an alternator and battery.

The other condition of a continuously discharging battery can be a back flow of voltage through the alternator's diodes. Normal checks at the parts store will not reveal this condition. One way to check is with the engine off, and all other electrical systems off, disconnect the alternator wire where it connects to the battery, with a VOM connect the ground side to the alternator wire and the positive side to the battery's positive terminal, if a voltage is present, one, two or all 3 diodes are leaking backwards current.

Keep in mind that these computer intensive modern vehicles are always using low levels of power to maintain memories, keep security systems running, keep the radio from loosing it's preset stations, etc. As the battery ages it looses it's ability to keep all this up even though the drain is small.

Bogie

Did you have the battery tested while you were there ?


Cole