Hunter Pro-C No Output To Zone Fault Tree

Why this matters

A single station on a Hunter Pro-C that will not energize (no water, while every other zone runs) is one of the most common irrigation service calls, and it has a short, ordered fault list that runs from the valve in the ground back to the controller's triac. Working it out of order wastes the visit: techs dig up a healthy valve when the fault was a 24 VAC station-terminal failure, or replace a controller when a corroded splice was the whole problem. The Pro-C reports a station-short fault on its display, which is a major clue, and a multimeter at three points (solenoid, field wire, controller terminal) isolates the break in minutes. Getting the sequence right turns an hour of digging into a ten-minute fix.

Symptom presentation

• One station does not run; the rest are fine.
• Pro-C may flash a station number with "Err" or show a no-output condition; a shorted solenoid/field wire typically triggers the controller's electronic short detection and skips that station.
• No water at the zone heads, valve does not click open, no audible solenoid pull-in.

Quick checks

1. Read the display. A Pro-C "Err" with a station number indicates the controller sensed a high-current (short) fault on that station and shut it off to protect the triac. No "Err" but no output points more toward an open circuit (broken wire, dead solenoid coil, bad terminal).
2. Confirm it is one station only. Multiple dead stations sharing a symptom point at a common-wire fault or master-valve/pump-start issue, not a single zone.
3. Manually run the station from the controller (Manual-Single-Station) so you are testing output, not the program schedule.
4. Have a multimeter ready for AC volts and ohms.

Isolation tree

Work from the controller terminal outward, measuring as you go.

• Measure 24 VAC at the controller between the station terminal and COM while that station is manually on.
  • No 24 VAC at the terminal -> controller-side fault. Sub-branch: the station's triac/output failed (often from a prior field short the controller could not fully protect against), the terminal screw is loose/corroded, or the station has zero run time/skip programmed. Confirm by moving the field wire to a known-good unused station terminal and reassigning; if it works there, the original output is dead (replace the output module or controller). The Pro-C output stage is the suspect here.
  • 24 VAC present at the terminal -> controller is fine; fault is downstream. Proceed.
• With 24 VAC confirmed at the terminal, measure 24 VAC at the valve (across the solenoid leads) while the station runs.
  • No/low voltage at the valve -> open or high-resistance field wiring: a broken station wire, a corroded or failed splice (the leading cause; underground wire-nut splices corrode), a rodent-chewed wire, or a bad common at that valve. Confirm by ohm-testing the field wire end-to-end. Repair the splice/wire with waterproof connectors.
  • 24 VAC present at the valve solenoid -> wiring and controller are good; the fault is the solenoid or valve itself. Proceed.
• Ohm-test the solenoid coil (disconnect leads, measure resistance). A good Hunter solenoid reads roughly 20 to 60 ohms (varies by model).
  • Open (infinite ohms) -> burned-out solenoid coil. Replace solenoid.
  • Very low / near-zero ohms (shorted) -> shorted solenoid; this is what trips the Pro-C "Err" short detection. Replace solenoid. After replacement, clear the controller fault and re-test.
  • Coil reads normal but valve still will not open -> mechanical valve fault: debris under the diaphragm, a stuck/clogged solenoid plunger, a closed flow-control/bleed screw, or a failed diaphragm. Clean or rebuild the valve.

Confirming diagnosis

The three-point voltage walk is definitive: 24 VAC absent at the terminal isolates the controller output; present at the terminal but absent at the valve isolates the field wiring/splice; present at the valve with a dead or shorted coil isolates the solenoid; present at the valve with a good coil isolates the valve mechanics. For a controller-short fault, swapping the suspect field wire to a known-good station terminal and seeing it work (or seeing the "Err" follow the wire) cleanly separates a controller-output failure from a downstream short. Always clear the Pro-C fault and re-run after any repair to confirm.

Remediation

• No 24 VAC at terminal: reseat/clean the terminal, reassign to a spare station if the triac is dead, or replace the Pro-C output module/controller. Confirm the station has run time and is not set to skip.
• No voltage at valve: find and repair the open field wire or corroded splice with waterproof (gel-filled) connectors; replace damaged wire runs.
• Open or shorted solenoid: replace the solenoid; clear the Pro-C "Err" and re-test.
• Good coil, valve won't open: clean debris from the diaphragm/solenoid port, open the flow-control and bleed, or rebuild/replace the valve.
• Document the repaired station and re-run the full program to confirm no remaining faults.

References

• Hunter Industries, "Pro-C Owner's Manual and Programming Instructions" (station error/short detection and manual operation).
• Hunter Industries, "Solenoid and Valve Troubleshooting" technical bulletins (coil resistance values).
• Irrigation Association, "Irrigation System Troubleshooting" (24 VAC field-wiring diagnosis).
• Hunter Industries valve installation and service instructions (PGV/ICV diaphragm and solenoid service).