The Case IH 3063978R91 is an original equipment manufacturer (OEM) contactor designed for electrical systems in a wide range of International Harvester and Case IH tractors. This essential electrical component ensures reliable power switching. It has been superseded by part number 3063976R91, which serves as a direct replacement. This contactor is compatible with models including 706, 756, 766, 806, 826, 856, 966, 1026, 1066, 1206, 1256, 1456, 1466, 1468, 1566, 1568, 21256, 21456, 2504, 2544, 2706, 2756, 2806, 2826, 2856, 4100, 4156, 4166, 4186, 4366, 4386, 4568, 4586, 4786, HYDRO 100, and HYDRO 70.