Lightning Strike on Irrigation System: Testing Controller & Valves

After a suspected lightning strike, systematically test the controller and each valve solenoid before replacing components. Most controllers have sacrificial protection (MOVs, fuses) that may have done their job.

Controller Assessment

• Display normal, programs run: Controller likely survived.
• Display garbled, blank, or erratic: Microprocessor damaged. Replace controller.
• Test zone outputs: Manually activate each zone; measure 24–28 VAC at terminals.

Valve/Solenoid Testing (Without Special Tools)

1. With controller powered, manually activate zone 1.
2. Listen/feel for solenoid click at valve box.
3. If click but no water: diaphragm or supply issue.
4. If no click: measure voltage at solenoid leads (24 VAC expected).
5. No voltage at solenoid but voltage at controller → wire break.
6. Voltage at solenoid but no click → solenoid failed (replace).

Built-In Protection

Quality controllers (Hunter, Rain Bird, Irritrol) have:

• Metal oxide varistors (MOVs) on zone outputs
• PTC resettable fuses or replaceable glass fuses
• Opto-isolated zone drivers (higher-end models)

These often sacrifice themselves to protect the microprocessor. A blown fuse = $2 fix. Fried MOV = controller replacement.

Practical Test Sequence

1. Replace controller fuse if blown.
2. Run each zone 2 minutes from controller.
3. Note which zones work vs. fail.
4. For failed zones, test solenoid resistance at valve (20–60 Ω good).
5. Replace only faulty solenoids.

When to Call Pro

If mainline wires were hit (direct strike to buried cable), insulation damage may be widespread. A wire locator and megohmmeter test can assess. Homeowner policies often cover lightning damage—document everything.