Troubleshooting a “Possessed” Zone Valve That Runs With Every Station

An 8-zone Irritrol system: whenever any zone runs (manual or auto), zone 7 also runs for the same duration. Disconnecting zone 7’s wire at the controller stops it. Valve 7 operates normally otherwise. No obvious wiring faults.

Likely Causes

1. Controller terminal fault – the zone 7 output may be leaking voltage.
2. Master-valve wiring confusion – if zone 7 wire is on the MV/COM terminal, it acts as a master valve.

Diagnostic Steps

• Move the zone 7 wire to a different terminal (e.g., zone 8) and see if the problem follows the wire or stays at terminal 7.
• Check controller station count—ensure zone 7 isn’t programmed as a master valve.
• If the issue stays at terminal 7 regardless of wire, the controller’s output driver is likely faulty.

Report back with results; a controller replacement may be needed.