The plunger is missing or stuck in the up position. Remove and inspect the solenoid.
Diaphragm filter plugged. This will prevent water from entering the upper chamber.
Flow control turned up too high. The diaphragm can stick in the up position under low flow/low pressure conditions.
Constant voltage from the controller. The solenoid will usually be warm to the touch and a slight vibration can be felt if this is happening.
Leak between the bonnet and body. Water will be visibly leaking where the body and bonnet are connected
An open manual bleed. An open external manual bleed will be very obvious. An internal manual bleed system can be unknowingly activated if the valve is unfamiliar to the customer.
A large hole in the diaphragm. (Forward flow valve only). Sufficient force will not build up in the upper chamber. Remove the diaphragm assembly and inspect it very carefully, replace it if there are any bubbles or other signs of wear.
The valve is installed backwards. The valve is now an expensive coupling. The arrows on the valve body indicate the direction of water flow through the valve.
Valve seeping - This is usually indicated by a puddle at the lowest sprinkler head. Using an automotive stethoscope may aid in determining which valve is leaking in a manifold. There are two main causes for this to happen.
Solenoid or solenoid seat is damaged. Water will constantly leak past the plunger. Replace the solenoid plunger of the seat if possible.
Valve seat is damaged. Check the valve seat and the diaphragm seating area for pitting and small debris. Replace the diaphragm if damaged. It may be necessary to replace the valve body if the seat area is damaged.
Valve will not open - There are again two main causes of this problem.
The first cause is an adjustment problem. The flow control stem is tightened all the way down.
The second is that the force is not being released from the upper chamber. There are several reasons for this to happen.
Solenoid burned out. A resistance test will verify if the coil is bad or not. Refer to the volt ohm-meter section to learn how to perform this test. Replace if necessary. 2. A torn diaphragm. (Reverse flow valve only). The hole in the diaphragm will allow more water into the upper chamber than can be bled off through the solenoid port. Inspect the diaphragm, and replace it if necessary.
Plugged ports. The port below the solenoid and/or the port leading to the solenoid chamber is plugged. This would again prevent the water in the upper chamber from being relieved. Clean the ports with a paper clip, never drill out the ports.
Solenoid not receiving voltage. The controller is not sending the necessary voltage, there are wiring problems, or the wire connections are faulty. Refer to the volt ohm-meter section to learn how to inspect the field wiring. 10