Dear customer,

 If unplug the power adapter, the zone is still watering, this zone valve needs to be checked. 

You can also switch this issue zone wire with other good zone wire. For example, assume the issue zone is zone 1, zone 2 is good zone. Switch zone 1 wire to zone 2, and zone 2 wire to zone 1. Test the two zones, see if the physical issue zone still faulty. 

Thanks,

Wency

Netro Support