[Andy]

yes one knock down and that should be in auto mode which you can then adjust the intermitance of the wipers by turning the dial on the wiper arm.

if not then you have a problem, poss faulty rain sensor on the windscreen behind rear view mirror, biggest cause of damaged rain sensors are if the windscreen has been replaced and sensor gets knocked or not repositioned right, or the wrong windscreen gets fitted and doesnt have the access area on the windsceen for the sensor to work......................intermitant auto mode still relys on water hitting the screen/sensor for them to operate.