I'm not much of a sprinkler guru so any help would be greatly appreciated. Here's my problem. When I plug in my sprinkler controller/timer, one of my zones opens up and won't shut off. When I unplug the controller, it closes again even with the water supply still on, so I don't think it's a problem with a grain of sand or anything keeping it open.

I wouldn't think that there should be power to the zones unless the timers are turned on, but they are all turned off. When I plug in the controller, with all the timers turned off, the solenoid in the yard for that particular zone starts buzzing and opens the zone and won't shut off unless I unplug the whole control unit.

Any and all help will be appreciated. By the way it's a Toro sprinkler system in case that matters.

Thanks.