What is the first thing to check if no zones operate from the controller?

When no zones operate from the controller, the first step is to check the power supply to the controller. This is critical because without power, the controller cannot send signals to open valves or activate any sprinkler zones. If the power supply is interrupted or faulty, the entire irrigation system becomes inoperative, rendering all other functions inactive.

After ensuring that the power supply is functioning correctly, other factors can be addressed, such as the programming settings, wiring connections, or water source availability. However, none of these will matter if the controller itself is not receiving power. Thus, verifying the power supply is the foundational step to troubleshoot the issue effectively.