[londonrain]

Please describe what is malfunctioning on the system.

 

[londonrain]

My experience with 2wire systems is that when the decoders go bad they either come on with every zone or they are completely dead, this is assuming the controller is operating correctly. I would start with the zones that will not shut off, either flow control the valve closed or disconnect one wire going to the solenoid. Once you get all the zones shut that want to come on regardless which zone is programed, then you can figure out which decoders are dead. You might now find zones that you think are not working are now working because you now have full flow to the zone valve. Also remember that the field wiring is always putting out 24v to all the decoders and you can check to see if the wire is providing 24v before the decoder. Do all of the above and report back!!!

 

[londonrain]

Nothing stuck on, but there were several alarms showing on the controller.
They have checked voltage, etc. at the valves and it's ok.
I suppose I need advice from someone who's familiar with the Toro system.
The problem seems to be intermittent communication between the controller and the decoders.
Nobody can figure out what's causing it. The current theory is interference from crossing a power line too closely. Is that a plausible explanation? They used the specified wire but it's not shielded.
The controller has diagnostics, but when you run them, different stations show a fault on different diagnostic runs.
The controller puts out 38 volts BTW. Anything between 12 and 38 volts is acceptable.
Thanks again

Sounds more like a wiring problem than a interference problem.
Since the TDC uses DC latching solenoids then the wiring must be correct for the solenoids to work correctly...IE: same color wires connected throughout the entire systems with correct wire splices plus the 2 wire cannot be looped back to the controller.......

 

[londonrain]

Sounding more like a serious wiring problem more than a hardware problem...... Since the 2wire is sending a signal ALL connections MUST be solid..... I have worked on many large community wide systems with 100+ zones and have found wires that had been cut during construction and electrical taped back together, this is the vibe I am getting on your system....... Find a contractor who understands how a 2wire system works and understands how to trouble shoot a 2wire, has a 521 locator and a ground fault locator....only thing you can do at this point is check and repair wires... or call in a JDLGreentech, I know my local Greentech helps with 2 wires systems.