An engine driven pump 24 is connected with a power steering motor assembly 18. An electric motor 36 drives a pump 34 connected with the power steering motor assembly 18. A control apparatus 38, 44, 52, 62 and 72 effects operation of the electric motor 36 to drive the pump 34 when the power steering motor assembly 18 requires fluid in addition to fluid supplied by the engine driven pump 24.