I HAVE A 1998 OLDS BRAVADA WITH THE 4.3 ENGINE. TO GET STARTED I HAD THE CAR TESTED BY TWO MECHANICS AND THE COULDNT FIND A PROBLEM. I TOOK IT TO HAVE THE CHARGING SYSTEM CHECKED AT AUTOZONE. THE BATTERY,IS NEW AND THE TEST SHOWED THE ALT,STARTER,AND BATTERY ALL CAME OUT GOOD AND CHARGING AT GOOD LEVELS THE BELT AND TENSION ARE WORKING PROPERLY ALSO AND IN GOOD SHAPE. THE PROBLEM I HAVE BEEN NOTICING IS JUST BEFORE THE CAR TURNS OFF I NOTICE THE BATTERY GAUGE DROPPING TO A LOW LEVEL AND POPPING BACK UP TO NORMAL LEVEL. IT WILL DO THIS A FEW TIMES AND THEN IT WILL DROP DOWN AND THE CAR WILL SHUT OFF. THE BATTERY LIGHT WILL COME ON JUST AS IT DIES. I PUT THE IGNITION IN THE OFF POSITION AND TURN IT ON AGAIN AND IT STARTS RIGHT UP. SOMETIMES IT CRANKS A FEW TIMES AND THEN STARTS AGAIN BUT USUALLY IT STARTS RIGHT UP. I FEEL LIKE IT COULD BE AN ALT PROBLEM BUT CAN IT BE SOMETHING ELSE.
JUST TO LET EVERYONE KNOW I DONT HAVE ANY BLOWN FUSES OR SHORTS CAUSE I CHECKED ALL THAT OUT AND THE BATTERY CABLES ARE CLEAN AND WIRES ARE ALL IN GOOD CONDITION NO CORROSION OR BURN MARKS ANYWHERE. I ALSO DONT HAVE ANY DVDS,TVS,AMPS, OR EXTRA STUFF HOOKED UP. THE ONLY THING I HAVE IS THE ALARM AND ALL THE POWER STUFF WORKS FINE. ALL THE MAINTENENCE IS UP TO DATE I DID THAT STUFF BECAUSE THE WINTER IS COMING UP SO IM LOST AS FAR AS THIS PROBLEM GOES ITS BEEN DOING THIS FOR ABOUT A YEAR AND ITS NOT ALL THE TIME IT DOES IT MAYBE ONCE OR TWICE A WEEK AND ALWAYS STARTS UP. I JUST DONT WANT TO CHANCE IT NOT STARTING UP AND LEAVE ME STRANDED IN THE MIDDLE OF NOWHERE.
I may have missed a few things. Trying to read a message IN ALL CAPS and without paragraphs is difficult.
My guess is you are having a problem with the ignition switch.
Take a look at your key ring. How many keys and doodads are on it? Extra weight on the key ring can damage an ignition switch.
If the alternator has a number of years use, it could be the worn alternator brushes bouncing out of contact with the rotor. Could be. Here is a repair kit ($50) for much less than a re-manufactured alternator would cost ($175): http://www.partsamerica.com/productdetail.aspx?MfrCode=VLP&MfrPartNumber=GMA04