I have 2002 Chev Silverado V8 221000 miles I have been the only owner no major problems with truck until now. Voltage meter started bouncing between 14 and 9, other gages started acting up,all except the oil pressure gage worked fine, lights were going dim, got home, truck died. Put on charge over night got to repair shop. Mechanic said the alternator was fried. Before all this put in a new battery. He put new altenator on but did the same thing with the voltage from 14-9. He said he will check wiring and the computer. Anyone have any ideas what may cause this. Truck has been very well taken care of. He said belts were fine. Thanks
This sounds like a voltage regulator problem. Unfortunately, the voltage regulation is controlled by the computer.
Sorry tester I type slower than you!
First stab at the cat would be a voltage regulator, after checking cables and seeing if there is a fried component kicking in causing a massive voltage drain. Some things you can do are turn off everything possible, heat fan defroster etc, and see if it still happens. If it does not start turning on fan, ac, etc. to see if you can isolate the source.
Verify with meter at battery.
If everything else checks out fine, consider a failing belt tensioner, glazed belt, or even a funky pulley on the alternator not getting a bite on the belt.
This could be verifed by attempting to turn the alt. pulley with a socket with the belt in place. The pulley should not move. If it slips with a socket/ratchet then there’s a belt, tensioner, or pulley problem.