1997 Ford F-150 • 118,234 miles  While drive and stopping at a
red light the head lights and int lights flicker I had the
alternator checked they said it was good but I'm stumped I have
checked almost evey thing and don't know what it is and also it
make a slite wine noise can u help me out the truck has bin well
taken care of March 21, 2013.  How was the generator tested? If
it was tested for voltage, that will be normal even if it has a
bad internal diode. One bad diode out of the six will reduce the
generator's maximum output current to exactly one third of its
rating. That's not enough to run the entire electrical system
under all conditions. You need to have the charging system
professionally load-tested to identify a bad diode. Besides the
output current that will be too low, "ripple" will be very high.
The brushes in the generator can be worn too and making
intermittent contact. They are bolted to the back-side of the
voltage regulator and can be replaced separately without
replacing the entire genera