This is generally because of a ruptured or torn diaphragm in one or more of the control valves. Be sure that the valve is not installed backwards. Make sure the solenoid plunger is not stuck or missing. Remove the solenoid and check for debris or a missing plunger. If everything looks functional, remove the cover assembly and check the diaphragm and lower valve body diaphragm seat for chips, fractures, or debris. If the diaphragm is torn, ruptured, or has a tiny pin hole, replace it. If there is a chip or fracture in the lower valve body, replace the valve. For additional help, refer to the troubleshooting section of the specific valve model number.