SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

You should probably get a multimeter,autoranging. Your a do-it-yourselfer and this will come in handy with all kinds of stuff. Doesnt matter which color of the multimeter lead you put where. I will just explain it like it does.
First shut clock off,turn meter to ohms. Open the controller up, put the RED lead onto the common "C" terminal,white is most likely the color. Then put BLACK lead onto each zone, while keeping RED lead on common. you will see a reading of about 35 on Irritrol valves, not positive though. With RED on the common terminal screw in clock,touch Black to each zone terminal. You will almost certainly see the readings go, 1=35 ohms 2=35.4 ohms 3=34 ohms 4= 36 ohms 5= (95.07) 6,7,8,9 will be normal, then 10= (110 ohms) of course zones 5 and 10 are the bad ones so you will need to get 2 new valves.This is most likely your problem,its common with Irritrol jar tops,I didnt look up the 311 model but Im assuming its the one im thinking of.
I would definately recommend just unscrewing the tops and replacing the whole valve,as opposed to just the solenoid. Shut your water off,bleed some of the zones on manually,clear out the dirt from around the pipes and valves in the valve box. When you open up the valve,its going to empty the main line BE READY.So obviousely if dirt is half way up the valves,the water has to go somwhere and it will fill the box,and the open valves with dirt.
Keep track of the red or grey diaphram seat,its a plastic circle piece,this goes in first,use the new one too dont reuse the old one,then the black rubber diaphram slides down the needle,then the spring sits in the middle,there is a spot for it to sit on,then the part with the solenoid goes on, and will usually hold itself on the valve but not always,then the screw down ring. tigten securely. Wire back up the way it was,doesnt matter which of the 2 wires on the solenoid goes where,as long as you put one to the common,and the other to the color the old solenoid wire was cut from,dont cut the old solenoid wires until you have the new valve installed,if you do cut it,cut the COLORED wire so that it will still be attached to the solenoid for easy checking.
If you do not get an unusual ohm reading on zone 5 and 10. Then check for voltage at the terminal. Red on common terminal,and black on zone 5,you test volts with zone 5 ON at the controller. Just never test for OHMS with power going to the zone,basically just shut the clock off when testing for ohms,the meter supplies its own power for ohm testing, and its not 24 volts,you can ruin the internals if you send 24 volts into your meter.
With RED on common and BLACK on whatever zone you have on 5 and 10, you should get APX 24 volts. If you dont its probably the clock that has the problem,terminals occasionally go bad,its rare though.If you do have apx 24 volts. It would most likely be a cut wire somwhere.Or a bad common splice or zone splice,go out and redo your connections. There are 2 wires on every solenoid,1 goes to a colored zone wire, the other to the common,if you have 5 valves in a valve box,and your common is white in the clock, White in the valve box will have 1 wire from each solenoid spliced into it. the other 5 wires go to its specific colored zone wire. let us know what happens