Resolving "Master Valve" Errors on Irritrol Controllers

What the Master Valve Error Means

A "Master Valve" error on an Irritrol (or similar) controller typically indicates a short in the master valve circuit—either in the wiring or the solenoid itself.

First Steps: Reset the Controller

1. Remove the 9 V backup battery (if present).
2. Disconnect AC power for 60 seconds.
3. Reconnect power, reprogram, then reinstall the battery.

Check for a Master Valve Installation

Not all systems have a master valve. Look at the controller terminals: if a wire is connected to the MV (or PS) terminal, a master valve is installed. This valve must open before any zone valve can operate.

Locate and Test the Master Valve

• Usually near the main shutoff valve for the irrigation system.
• Test solenoid resistance (20–60 Ω typical) and inspect wiring for nicks or corrosion.
• Manually activate the valve using its bleed screw to confirm mechanical operation.

Common Causes

• Solenoid failure (most common).
• Wire short to ground or common wire.
• Controller output triac failure (less common).

If the error persists after solenoid replacement and wiring inspection, the controller may need replacement.