A differential control valve comprising: a housing having an interior surface defining an internal chamber with a central axis (A-A); a first valve seat disposed along the interior surface of the housing circumscribed about the central axis (A-A); a second valve seat disposed along the interior surface disposed and circumscribed about the first valve seat; a seal member defining a sealed position engaged with the first valve seat and the second valve seat, the seal member further defining an open position axially spaced from the first and second valve seats (24,26), the seal member being substantially aligned with the central axis (A-A) of the housing in each of the sealed and open positions; a first port proximate the first valve seat in communication with the internal chamber, and a second port in communication with the internal chamber, the second port being isolated from the first port when the sealing member is in the sealed position and in fluid communication with the first port when the sealing member is in the open position; at least one spring member disposed between the interior surface of the housing and the seal member to bias the seal member toward the open position; characterised in that the valve further includes: an elongated plunger member engaged with the housing so to have a portion disposed in the internal chamber, and wherein the seal member includes a receptacle for receiving the portion of the elongated plunger member to locate the seal member in the sealed position. a housing having an interior surface defining an internal chamber with a central axis (A-A); a first valve seat disposed along the interior surface of the housing circumscribed about the central axis (A-A); a second valve seat disposed along the interior surface disposed and circumscribed about the first valve seat; a seal member defining a sealed position engaged with the first valve seat and the second valve seat, the seal member further defining an open position axially spaced from the first and second valve seats (24,26), the seal member being substantially aligned with the central axis (A-A) of the housing in each of the sealed and open positions; a first port proximate the first valve seat in communication with the internal chamber, and a second port in communication with the internal chamber, the second port being isolated from the first port when the sealing member is in the sealed position and in fluid communication with the first port when the sealing member is in the open position; at least one spring member disposed between the interior surface of the housing and the seal member to bias the seal member toward the open position; characterised in that the valve further includes: an elongated plunger member engaged with the housing so to have a portion disposed in the internal chamber, and wherein the seal member includes a receptacle for receiving the portion of the elongated plunger member to locate the seal member in the sealed position. an elongated plunger member engaged with the housing so to have a portion disposed in the internal chamber, and wherein the seal member includes a receptacle for receiving the portion of the elongated plunger member to locate the seal member in the sealed position.