What was found
LEFT AND RIGHT ALTERNATOR BELTS WERE REPLACED WITH NEW BELTS AT PROPELLER OVERHAUL. WITHIN APPROXIMATELY 3 HRS, THE RT BELT FAILED DUE TO UNKNOWN REASONS AND LT BELT WAS SLIPPING DUE TO METEROLOGICAL CONDITIONS WHICH RESULTED IN LOSS OF ELECTRICAL POWER. RE-ADJUSTED TENSION ON LT BELT AND INSTALLED NEW BELT ON RT SIDE AND ADJUSTED TENSION. PERFORMED ABOUT A 15-MINUTE RUN-UP AND RE-CHECKED TENSIONS. RECOMMEND CHECKING BELT ALIGNMENT AND RE-CHECKING BELT TENSION AFTER A GOOD GROUND RUN.