As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOSS OF LEFT ALTERNATOR FOLLOWED BY LOSS OF DEICE COMPONENTS LEAD PILOT TO TAKE EMERGENCY ACTION IN IMC AND DIVERT BACK TO ORIGIN. UPON INSPECTION FOUND LEFT ALTERNATOR BELT TENSIONER BOLT TO HAVE LOOSENED UP, CAUSING THE LEFT ALTERNATOR BELT TO BECOME LOOSE. THUS CAUSING AN ALTERNATOR FAILURE. BATTERY WAS CHANGED OUT WITH NEW AS A PRECAUTIONARY MEASURE.