My yard's irrigation has a total of 8 zones (two irrigation boxes of 4 zones each). After turning on the irrigation this year, I noticed that one whole irrigation box (4 zones) all won't turn on, while the other does. I have had one zone fail before and I've had to replace a solenoid, but never all 4 fail. I tested the electrical wires on each valve and confirmed each one is getting 24 volts. Next, I tested the resistance of each solenoid and confirmed they were each 25 ohms. Also, I can turn the solenoid a quarter turn, or open the bleed screw, and each valve manually turns on.
Now I'm at a loss at what to do next. I would assume that it's likely not a valve problem, as all 4 valves won't open. It seems more likely to be an electric problem, but the proper voltage seems to be getting to the box. What else can I check to diagnose the problem?