As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) OUR STANDBY ELECTRICAL POWER INOP LIGHT WAS FADING IN AND OUT AT APPROX 65 - 67 PERCENT NG. THE RESISTOR WAS CHECKED OUT AT 110 OHMS AND THEN THE FIELD BRUSHES WERE CHECKED - FOUND THAT TO BE WORN PAST THE POINT OF MAKING CONTACT WITH THE SLIP RINGS. NEW BRUSHES WERE INSTALLED AND THE PROBLEM DID NOT RETURN.