Suddenly one of the sprinkler system zones does not stop when time expires. It remains open. I had to manually shut off water supply after time for all zones expire. Any help will be appreciated.
Thanks.

I would bet that the plunger in the solenoid on the valve for that zone is stuck. There might be a tiny bit of debris caught in the chamber. First of all, TURN OFF the water to your system. Then, identify which valve is responsible for that zone. The solenoid is the round thing on the top of the valve with two wires coming out of it. Unscrew the solenoid and remove it carefully. Newer control valve solenoids have what's called a "captured plunger" which simply means the plunger won't fall into the dirt or gravel so you can't EVER find it again. The older solenoids will do exactly that if you aren't careful. Check to see if the plunger moves up and down freely within the chamber/tube inside the solenoid.
If it doesn't, you'll have to remove the round part which holds the solenoid inside and swish the whole thing in a cup of water to clean it. Now, if the plunger does move freely, it might be something else. In that case, check the end of the solenoid which is supposed to keep the valve closed. It's usually a little white/cream colored circle on the end of the plunger. If there's a deep circle shaped groove in the white part, it just means that the plunger isn't seating and sealing so the valve can close. You might be able to find an irrigation supply house nearby that would have just a plunger on hand. Otherwise, you might have to buy a new solenoid -- and, if that's the case, sometimes a whole new valve is a better buy. NOT to replace the whole valve--just to cannibalize the valve for a solenoid/plunger. Sounds nuts but sometimes a solenoid can cost as much as the whole thing. Good luck!