Turn the controller to " System Off" so it does not try to cycle a program.
Shut off the main water supply. Opening a valve under pressure is dangerous and you could be injured.
Unscrew the solenoid (cylinder with two wires) and make sure the plunger is clean and moves freely. You can test the solenoid by running that station manually from the controller and see if the plunger retracts when energized.
Unscrew the bonnet screws or jar top depending on your valve model. Be careful when you pull the bonnet away from the body as to not loose the diaphragm or spring.
The diaphragm may be sitting in the body or captured in the bonnet. Remove the diaphragm and spring. Make note of the orientation of the diaphragm so you can put it back together the same way it came out.
Examine the diaphragm and spring. The diaphragm should be clean and free of wrinkles, tears, or perforations. The seal should be clean and free of nicks, dents or abrasions. Wash the diaphragm with clean fresh water to remove any debris that may have been deposited there.
The diaphragm spring should be intact and bounce back when compressed.
Examine the valve body and remove any debris, pebbles, or dirty water.
The seal seat should be clean and free of nicks, grooves, or abrasions.
Examine the porting in both the valve body and the bonnet. All ports should be clear and pass water freely. A small piece of flexible wire can be passed through the ports to remove blockage.
Reassemble the valve in the reverse order of how it was taken apart. The diaphragm should sit with the lip in the matching groove on both the body and the bonnet. The screws or jar top should be hand tightened. Over tightening can damage the valve.
If you are still experiencing problems with your valve, you may need to contact a local professional by clicking on the following link.