Sadman,

You have the right idea. Hire a landscaper who is experienced with irrigation system. He can pinpoint where the chattering is actually coming from. It could be caused by many problematic things. A couple of things to try though. Make sure your main water source valves are fully open. Do you have any check valve or any other restrictive fittings in your system? Without using your controller slightly unscrew the solenoid and see if the zone starts up. Do you still hear the chattering? Listen close to what part of the valve is making the noise. Is it all the valves or just a few? Screw down the solenoid enough to turn off the zone and try again from the controller and see if the sound continues. If it does call the experts. Let us know here how it goes. JMHO Aloha

Aloha JMHO - Water pressure - The valves are open, and I've checked my water pressure with a tester on various hose bibs. It seems to be between 45 - 50. Shouldn't that be enough to drive one valve with 4 sprinkler heads? I don't think my water pressure has really been any higher. If so, I think I can rule out low water pressure, which means it's back to wiring or the timer..... What do you think?

I also replaced one of the existing valves with a new valve actuator component and tested it. So, with that new valve it included new solenoid, diaphragm, everything. And, the brand new one chatters as well.

Back to needing an expert....

Aloha JMHO again - I actually bought a couple of those actuators. So, I just went to the timer, turned on a valve, then touched the live wire and the ground of my new actuator to the appropriate connectors on the timer. And, that new actuator chatters right at the timer! Doesn't that mean that the timer is shot??

Sadman,

The amazing thing to me is that you read my post and totally ignored it. I didn't mention anything about pressure and the more you explain the more confused I get about what you are actually experiencing. That is why hiring a local irrigation guy or talking to an experienced friend to look at your setup will be far more productive and hopefully fix your problem quicker than the back and forth process on this thread. I have no idea what you did at the controller with the wires. If it was appropriate or not and you seem in danger of being shocked or at least fry the controller. I don't understand the chattering you heard at the controller but it might be having a poor connection at the controller terminal from being hand held.

Are you describing an electrical chattering from the solenoid cycling on and off or water chattering through the valves or both? Your pressure is in the normal range for a good irrigation system to operate. Replace the controller and see if that stops it. The valve is probably opening and closing rapidly causing rapid water hammer. If all the valves are experiencing the same problem, it is most likely the controller with faulty connections or internal problems. (Just My Humble Opinion) Aloha

Usual cause is a timer going bad. A capacitor in the timer. Replacing or repairing the timer should fix it. It will get worse until it doesn't work.