An improved air flow direction control valve particularly adapted for use with an exhaust gas purifying system on an internal combustion engine to control the direction of flow of air to be mixed into exhaust gas for effecting additional combustion of the uncombusted constituents therein. The valve essentially comprises a pair of valve members selectively operable to open one of two main outlets and a diaphragm operated shaft for selectively operating the two valve members upon movement between a first and a second position. The shaft is formed with a pair of shoulders which define a reduced diameter shaft portion therebetween, and the two valve members encircle the reduced diameter shaft portion in an oppositely facing relation. The reduced diameter shaft portion is slidable relative to the two valve members and upon movement of the shaft axially into its first position, one of the shoulders thereof is engageable with the first valve member to open the first main outlet, while the other shoulder is engageable with the second valve member to open the second main outlet upon movement of the shaft into its second position. At least one coil spring is provided for urging either of the valve members not engaged by the corresponding shaft shoulder, into a position to keep the corresponding valve outlet closed. The valve further includes a third valve member which is resiliently supported to close an auxiliary valve outlet. According to one embodiment of the invention, the third valve member is operated independently of the shaft, while according to another embodiment, it is operationally associated with the shaft.