MAINTENANCE WAS DOING WEEKLY INSPECTION OF BRAKE WEAR LIMIT SWITCH AND UNIT WOULDN'T RESET. ELECTRICIANS WERE CALLED AT 2:40 P.M. AND THEY CHECKED CIRCUITS UNTIL THEY FOUND THE RELAY CONTACT C OIL ON UVM TO MAIN CONTACTOR WAS BURNED AND HAD TO BE REPLACED. WORK WAS COMPLETED AT 6:05 P.M. SAME DAY AND MSHA WAS CALLED AND TOLD HOIST WAS BACK IN SERVICE.