Check the small section of loom that runs from in the boot to the underside pump. Had a similar issue with mine a while ago and it turned out that one of the wires had frayed. If your goin to remove the bit of loom to inspect it, pull it thru with some string attatched to it, makes it a lot easier to feed it back thru if it turns out its not the wiring! Check the terminals on the pump too as your there.