Hayward pool pump motor, back cover made of metal affixes with two screws. Motor trips breaker with cover on, but runs fine with cover off. Have temporarily sealed the back of the motor by taping a plastic bag to it...pump runs fine. I know there may be a short caused by the metal cover, but cannot find black marks on the inside cover. Back of the motor is located close to a wall. Does anyone know if a replacement cover made of plastic is available?