Question
Jim; A friend has an older Toro system with a TMC212 controller. One zone does not shut off, all others work fine. I have not yet located the valves for the zones, however there are 4 devices mounted below the controller that look like solenoids and are wired to the controller. They have small tubing coming out of them which apparently go out to the valve locations and have a common tube (approx 1/4 inch) which also exits the garage and out to somewhere. Looks to me like some sort of pneumatic  system. These activate and buzz when each zone comes on. What are they and could one of these be part of the problem with the zone that stays on? Thanks George

Answer
Hey George, It sounds like you have a hydraulic system, the unit below the controller is a hydraulic conversion kit. The controller is actually for electric valves, so the conversion kit allows the controller to turn on a solenoid, which opens up, and allows the hydraulic valve to open. I would imagine that the valves in the ground are at least 40 years old, or the original ones would have been installed at least that long ago, they might have been repaired or replaced over the years. More than likely the problem is probably in the valve itself, and not the conversion kit. To tell if the problem is in the conversion kit, simply take off the tubing going to the bad valve and switch it with the tubing going to a good valve, (swap the tubes). Now if the bad valve is still stuck on, then the valve is bad. If the valve that you swapped the tubing with is stuck on, then the conversion kit is bad. I would suggest this as a long term solution. #1 Find the original hydraulic valves and replace them with solenoid valves. #2 disconnect the hydraulic conversion kit, and run new wires from the controller to the new solenoid valves. Hydraulic valves are getting harder and harder to find, and hydraulic controllers are no longer made, that is why you have the conversion kit. With the conversion to electric valves, you will always be able to find parts easily, and the valves can always be rebuilt instead of having to replace them. Good luck and have a great day.