Carefully clean everything, then reassemble the valve.
Some valves have a separate lid gasket or o-ring that needs to be cleaned or replaced before being reassembled. If there are any o-rings, I strongly suggest you lubricate them before reassembling using a lubricant. Lubricating o-rings is optional, but recommended as it keeps them from crimping during assembly. If the o-ring crimps it will be ruined and will leak. Use a water-based lubricant. Do not use vaseline, silicone, oil or any petroleum based products on the valve, they may damage the seals and also may clog the ports in the valve.
When attaching the lid, avoid striping out the lid threads and warping the lid as follows: When inserting the screws that hold the cap on, start with one of the screws next to the solenoid. Insert the screw in the hole then turn it counter-clockwise (losey lefty) until you feel a slight click as the screw finds the threads. Then reverse direction (righty tighty) and lightly tighten it. Then insert the second screw on the opposite side of the valve lid. Like the first, find the threads then just lightly tighten the screw. Continue with one screw on one side and the next on the other until they are all in. Now go back and tighten them all, going in the same order you inserted them. Do not over-tighten the screws on plastic valves, you will strip out the threads.
If you’re blessed and didn’t mess up something the valve should work correctly now.
Suggestion: Your valve has already failed once, chances are that means something in the water got stuck in it, which means there is sand or whatever in the water supply. Consider installing a filter upstream of the valve to keep out the sand and crud in the future. Typically the cost of a valve repair is greater than the cost of installing a filter. See the Irrigation Water Filtration Tutorial.
Provided free of charge for homeowners and professionals, these tutorials has been continuously refined since 1995 to teach professional irrigation methods. Although the content is optimized for Western U.S.A. environments, its scientific principles are applicable globally. By using this information, the user agrees that no warranties or guarantees are provided, and they assume all responsibility for the suitability of the design for their specific project.