The charging system went down in my 2000 Silverado (small V-8, 4x4, manual tranny). I replaced the battery and alternator and then figured out it was a defective isolator I had installed a few years ago because I occasionally tow a dump trailer which can draw current from the truck to charge its own battery. So after removing the isolator the system charges at 14 plus volts (with a new alternator) and the battery is fully charged BUT randomly the alt light comes on for a few seconds to about a minute at a time. It does it maybe twice per hour with no pattern I can detect, and when it comes on the alt is still putting out over 14 volts. Any ideas ????
John