A controller that will not step through its zones properly is more often misprogrammed than broken. Zones set to zero run time are skipped silently, multiple programs with overlapping start times chain into each other so the cycle appears never to end, and a station output stuck in the conducting state holds one zone on indefinitely. Only the last of those is a hardware fault.
Three different symptoms, three different causes
| Symptom | Usual cause |
|---|---|
| Stops after one or two zones | Remaining zones set to zero run time, or excluded from the active program |
| Skips specific zones every time | Those stations not assigned to the running program |
| Stuck on one zone indefinitely | Station output failed in the conducting state, or a valve stuck open |
| Cycles for hours and seems never to finish | Overlapping programs, or multiple start times chaining together |
| Restarts from zone one repeatedly | Several start times set in the same program |
| Advances but no water on some zones | Not a controller fault — those zones have valve or wiring problems |
| Stops partway after a power interruption | Program lost, running defaults, or a failed backup battery |
The overlapping-programs problem
This one deserves explaining because it is so common and so easy to create by accident. Most controllers support several independent programs, each with its own days, start times and zone assignments, and each program can usually hold multiple start times.
Set two start times in one program and the controller will run the entire sequence of zones, then run it again from the beginning. Add a second program overlapping the first and the controller queues them, running one complete cycle after another. From the outside this looks like a controller that has got stuck in a loop and will not finish, when in fact it is doing precisely what it was told.
The water consequence is significant — everything gets watered twice or three times — and it shows up on a bill without any visible symptom in the landscape beyond soggy ground. It is one of the first things worth checking when a bill rises with no leak to be found.
Zero run times and unassigned stations
A zone set to a zero run time is not reported as an error. The controller advances to it, finds nothing to do, and moves on in a fraction of a second. To a homeowner watching, the zone was skipped.
The same is true of a station that is not assigned to the program currently running. If zones one through six are on program A and zones seven through ten were put on program B, then running program A will always appear to stop at six. Nothing is wrong.
This happens most often on large systems — the twenty-zone properties common in Milton, Cumming and Johns Creek — where zones genuinely do need splitting across programs to fit inside the legal watering window. The split is correct; what gets lost is the record of which program covers what.
Want this looked at rather than read about?
Diagnostic-first visits across North Georgia. Call 770.335.8595 or request service — you get an estimate before any work begins.
When it is genuinely hardware
One symptom on that list is a real fault: a zone that stays on and will not release. Station outputs in modern controllers are solid-state switches, and one can fail in the conducting state, passing 24 volts continuously regardless of what the program says. The display looks normal while one zone runs forever.
The test is simple. Unplug the controller. If the zone stops, the controller was holding it on and the output has failed. If it keeps running, the controller is innocent and the valve is stuck open mechanically — a debris-fouled or torn diaphragm, or a bleed screw left open. See why a sprinkler zone will not shut off.
A failed output on one station sometimes gets worked around by moving that zone to a spare station, if the controller has one. Otherwise it means replacement, because a controller that cannot switch a zone off is a controller that will eventually leave one running unattended.
How the programming should be set up
- Write down what every station operates. Station number and the area it waters, kept inside the controller door. This is the single most useful piece of documentation on any irrigation system.
- Use one start time per program. Unless you are deliberately using cycle-and-soak, in which case the additional starts are intentional and should be recorded as such.
- Keep programs from overlapping. Work out roughly how long each program takes to complete, then space start times so one finishes before the next begins.
- Fit everything inside the watering window. Landscape watering with publicly supplied water is permitted only between 4 p.m. and 10 a.m. under the Georgia Water Stewardship Act. A large system needs staggered starts to complete inside it rather than being cut off mid-cycle.
- Use seasonal adjustment rather than rewriting run times. It scales every zone proportionally, which preserves the relative balance between them that someone worked out originally.
- Verify by running the whole program once, watching it. The only way to confirm a program does what you intended is to watch it do it.
Related answers
- My Sprinkler Controller Has Power But the Sprinklers Will Not Run. Why?A controller with a working display proves only that its logic board has power — it says nothing about whether 24 volts is reaching the valves or…
- How Should I Program My Sprinkler Controller in Georgia?Programming for North Georgia comes down to three things: schedule inside the 4 p.m. to 10 a.m. window that applies to publicly supplied water, split…
- Why Won’t My Sprinkler Zone Shut Off?A zone that will not shut off is either a valve that cannot seal or a controller that is still energising it. Unplug the controller: if the zone…
- Why Did My Water Bill Suddenly Go Up?If your water bill jumped and nothing about your household changed, an irrigation leak is the most likely cause, because a sprinkler system is the…
Services that fix this
Controller Repair
The brain of the system: no power, dead stations, lost schedules and surge damage diagnosed and repaired.
Read more →Irrigation Maintenance
Spring startup, seasonal adjustment and winterization — the work that stops repairs from happening.
Read more →Where we work
Irrigation Medics repairs irrigation systems across Hall County and the Lake Lanier communities, the Gwinnett corridor through Duluth, Suwanee and Buford, and North Fulton and Forsyth — Johns Creek, Alpharetta, Milton, Roswell and Cumming. Same rates throughout. See the service area.