british gas emp2 timer unit not working

[movinghomes]

emp2 central heating timer isn't turning off the hot water, sliding the button up or down wan't turn the hot water offf. checked the water unit on the watertank which opens the valt and closes the valt to turn it off works but the button at the unit on the wall dosn't tell it to turn and switch off the water.
can you help as the water is on constanly and costing me money.