Hey guys, I've got a 20 zone sprinkler system at my home. It's been working for 12 years now work just minor problems. All of a sudden, half of my zones will not actuate from the clock. They all work just fine manually operating the solenoids locally. I decided to take some voltage and resistance readings to try to diagnose the problem and found very interesting results.
​​​Common wire to any of the stations that do not work are showing an open. Common wire to the stations that do work are showing normal readings.
I also tried connecting the ground to one of the zone that do not work out at the irrigation box just to see if I have continuity (without power of course) and there was no continuity between them.
when turning on any of the stations that do not work, they ALL show voltage to ground, by just turning one on.
The resistance between the ones not working are all over the place, from 48 ohms up to 90 ohms.

I feel like I have a wiring problem. I haven't done any recent digging or anything like that.

 

"Common wire to any of the stations that do not work are showing an open." Sounds like you found the problem. You have a break in the wire or a bad connection. Often the wiring between controller and valves is a multi conductor cable. If you are lucky there are already conductors/wires there that are not being used so you can make one of them into a new common wire.

 

Common wires for each zone valve from the controller and from the zone valve solenoid are tied together in the zone valve box. Bad common wire connections in the zone valve box are common due to the wet environment unless soldered. If common wires are not soldered, solder them together.