battery level may be low or air lock in pipes causes this to happen
make sure first that battery is well charged
work with my brothers van
hope this helps
ray
May 2009
Bob Paine could be right but first check you haven't a pressure valve in the cold in supply near the inlet it's white with knurled knob on top. Turn the knob clockwise to close the valve then open a cold tap turn the valve until you hear a click THEN STOP turning turn off the tap and you should find the pump has stopped. This is common with pressure valves they need re-adjusting occasionally.
Bob Whiting
May 2009
as a temporary measure switch off the pump control above the door
These taps have a micro switch built in and the tap has to be removed to fit a new one.