Diagnosing Intermittent Zone Failures and Pulsating Sprinklers

Symptoms Escalate Over Time

System worked since April. Now: zone runs few minutes, shuts down, restarts, then subsequent zones pulsate—heads pop up for split seconds. No visible leaks. User suspects solenoid or wiring.

Diagnostic Steps Taken

• Zones 1-2 work; zone 3 fails; zones 4-5 fail.
• Skipping zone 3: zones 1-2, 4-6 work; zone 7 fails; subsequent zones fail.
• Skipping zones 3 & 7: no zones run.
• Working zones have good pressure—likely not a supply issue.

Valve Identification

Valves are Irritrol 205S. Each zone has its own valve+solenoid. Only 3 valve boxes found in front for 6 zones—backyard valves likely buried under grass.

Expert Analysis

The pattern suggests a faulty solenoid on zone 3 (and possibly zone 7) causing the controller's internal auto-reset breaker to trip, cutting power to subsequent zones. When the bad solenoid draws excess current, the controller protects itself by shutting down output.

Test Procedure

1. Disconnect zone 3 wire at controller.
2. Run system—if zones 1-2, 4-6 run perfectly, zone 3 solenoid is bad.
3. Repeat for zone 7.

Manual Valve Operation

Turn solenoid counter-clockwise 1/4–1/2 turn to open manually. The top screw is flow control—turn CCW 1 turn to increase flow if needed. Locate buried valves by probing for depressions in soil.

Next Steps

Test solenoids with multimeter (should read 20-60 ohms). Replace bad solenoids or entire valve tops. Check voltage at controller terminals during operation—should be 24-27 VAC steady.