As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT LOST ELECTRICAL POWER IN FLIGHT. PLUG THAT CONNECTED VOLTAGE REGULATOR/ WARNING INDICATOR TO ALTERNATOR DID NOT LOCK AND VIBRATED LOOSE. BECAUSE THE LOW VOLTAGE INDICATOR DIE NOT ILLUMINATE AND THE AMMETER IS ON THE FAR RIGHT SIDE OF CABIN, PILOT WAS UNAWARE OF PROBLEM UNTIL RADIO COMMUNICATION FAILED.