Question about 1997 Chevrolet Blazer

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Possible voltage regulator problem on alternator

97 chevy truck 5.7 liter 4x4 ac, auto 100,000 miles
There was a voltage drop on the dash gauge 9-10 volts. Had a load test done on the battery and alternator at Autozone with the truck running and under a load.. Battery checked out fine, but the alternator failed their test. Removed alternator (remanufactured) and had t tested on their bench machine and it passed 5 times. Just to be on the safe side I put in a new alternator. Since the voltage regulator is on the alternator could it be that the old alternator is failing but no tests are showing this. I have also checked all wiring for wear and ground shorts. Kind of stumped on this one. Am I missing some other electrical problem or part!
Thank you, Joel

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  • Anonymous Mar 26, 2014

    volt gauge shows no voltage key on or off


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Disconnect the battery, disconnect the red wire on the alternator stud, disconnect the (2) wire connector on the alternator. Reconnect the battery, turn the ignition to the run position, check both red wires and the brown at the alternator and make sure there is voltage on all wires.
Per your description, I believe you will not have voltage on one or both of the large red wires.
Let me know.

Posted on May 09, 2009

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I've always found the "weak spot" on GM side terminal batteries, to be the terminals (and the lil bolts that screw into them) Pop them out and Check to see if they are very clean and free of any corrosion ... I as a rule always check these first ... and generally replace the bolts and clean the terminals with a wire brush and battery terminal cleaner spray (or in a pinch coca cola) then water because they are usually not acceptable ... then I would ... in darkness turn the headlamps on while the truck is NOT running (a good battery should power the lights for at least 3- 4 hours before it goes totally dead) and after (20) minutes try to start it (if it cannot power the lights for twenty minutes and then start the truck ... charge the battery for at least overnight on a 10A+ charger ... and try again, replace battery if necessary) .... after it starts the lights should appear brighter ... and the gauge should go up to over 13 volts ... if there is no increase in brightness or voltage ... I would check to see that the field terminals are getting power .... also check to see that the mounting bolts are also clean at the alternator. Good luck

Posted on May 09, 2009

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