water pressure may be too low, try topping up. water pressure switch may be blocked, also on some early models the overheat stat, which has a manual re-set causes the same fault.
Ian
March 2010
F9 - Pressure -
water pressure connector loose/ unconnected/ faulty or wires trapped.
water pressure sensor faulty.
pump ceased/ faulty
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.