The problem here is likely to be a faulty micro-switch which isn't breaking the contacts properly after the valve has been driven open. The valve opens by turning a plug with a port in it (through which the water passes). The plug is turned through 90 degrees to let water pass through. When it closes it continues to turn the plug through another 90 degrees which shuts the water off. The plug also has an eccentric on it which opens and shuts the micro-switch. If the micro-switch sticks, it continues to supply power to the motor which turns the plug constantly through 360 degrees, which then keeps opening and shutting the port. I managed to prise my AC1+ open and then I worked the micro-switch open/closed for a dozen times and it cured the problem.
Tony Reid, May 2016
