Question
QUESTION: I have small lawn system with four Nelson valves running separate zones.  One of the zones will not shut off.  I have opened the valve and replaced the top half along with solenoid.  It makes a slight clicking noise as it something is trying to turn. Any ideas?

ANSWER: Hey Bob, I hope this helps. When you replaced the top half and the solenoid, did you also replace the diaphram? I would suggest to replace the diaphram, and also, when you have the diaphram out of the valve, inspect the bottom half of the valve to make sure it is not cracked, or has any debris in it. It sounds as if something might be stuck, or is rattling around in the bottom of the valve (clicking noise). The other thing that could be making a clicking noise, is the solenoid. In the center of the solenoid is a plunger, when the clock turns on the valve, the solenoid acts like a magnet, and pulls the plunger up to the top of the solenoid. This sometimes sounds like a clicking noise. If it is making this noise all the time, it could be the controller is shorting out, and is constantly sending a signal to open this particular valve. I would suggest disconnecting the power to the controller, and see if you still hear this noise. Well hopefully you have a good starting point, let me know if I can be of anymore help. Thanks and have a good day.

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QUESTION: Thanks for the advice.  I will try a new diaphragm and spring.  The replacement kits mention an 'O' ring also but I do not see where that goes.  Can you help me there?

As for the clicking noise it is only when I first turn on the supply line and and when the supply valve is only partially open.  When the supply is fully open it seems to stop the noise.

Thanks

Answer
Hey Bob, I hope this helps. Depending on the size of the O-ring, it either goes in the top hole where the solenoid threads into the top of the body, or if it is real small, it fits between the top half of the body and the bottom half of the body, directly in the center of where the solenoid screws in. Sorry but I'm not real familiar with this particular valve. Without full pressure on the valve, the diaphram is probably moving up and down making the noise you are hearing. Good luck and have a great day.