DURING THE 8:00 PM SHIFT CHANGE, THE RODEO HOIST WAS SHUT OFF. WHEN THE HOISTMAN ATTEMPTED TO RE-START THE HOIST, THE HOIST FAILED TO RE-START. THE ON-CALL ELECTRICAIN WAS CONTACTED AND REPAIR S WERE EXPEDITED. THE ELECTRICIAN FOUND A DIRTY CONTACTOR WHICH CAUSED THE FAILURE. THE CONTACTOR WAS CLEANED AND NORMAL OPERATIONS RESUMED AT 10:35.