Diagnosing a Pump That Cycles on One Zone Only

Symptom: Pump Short-Cycles on a Single Zone

If your pump runs 2–3 seconds on, 2–3 seconds off continuously when one zone is active (while other zones work normally), the problem is likely a stuck-open valve or a controller/wiring fault for that zone.

Isolate the Fault: Valve vs. Controller

1. Identify the valve for the problematic zone.
2. Disconnect the two solenoid wires at the valve.
3. Run the system through a normal cycle.

If the pump still cycles: The valve is mechanically stuck open (debris, torn diaphragm, or failed plunger). Rebuild or replace the valve.

If the pump runs normally: The controller or wiring is sending a continuous signal. Check for a shorted wire or a failed controller output.

Valve Rebuild Resources

Visit irrigationtutorials.com for step-by-step guides on disassembling, cleaning, and replacing diaphragms and solenoids for most major brands.

Preventive Note

Install a filter upstream of the valves if your water source contains sediment, which is a common cause of valve sticking.