Sprinkler Controller & Timer Repair

A sprinkler controller does one simple job: close a 24-volt AC circuit to one valve at a time, on a schedule. Everything else it offers — seasonal adjust, rain delay, multiple programs, WiFi — is layered on top of that. Understanding the simple job is what makes the faults diagnosable.

Three things can go wrong. The controller can lose incoming power, in which case the display is dark and nothing runs. The controller can have power but fail to deliver voltage to a station, which means one zone or all zones stay dead while the display looks perfectly normal. Or the controller can be working correctly and the fault lies out in the field wiring or at the valve — in which case replacing the controller changes nothing, which is exactly why we measure before we recommend.

Symptoms homeowners notice

• Display completely dark, no lights, nothing responds
• Display works but no zone runs when manually started
• Display works and most zones run, but one station is dead
• Programs reset themselves, or the time reverts after a power cut
• Zones running at unexpected hours, or the same zone running several times
• The system waters when it is raining
• A short circuit, fault or error message on one station
• The controller repeatedly blows its fuse
• A WiFi or smart controller that has dropped offline and will not reconnect
• Buttons or the dial no longer respond, or the screen is unreadable

The most likely causes

• Failed transformer. The transformer steps household voltage down to about 24 volts AC. It is the most common controller failure, and on many models it is a separate, replaceable part rather than a reason to replace the controller.
• No incoming power. A tripped GFCI, a switched-off outlet, a tripped breaker, or a chewed power cord. Always worth checking before anything else — it is free.
• Blown fuse or tripped internal protection. Almost always caused by a short in the field wiring or a shorted solenoid. Replacing the fuse without finding the short just blows another fuse.
• Lightning or surge damage. North Georgia gets frequent summer thunderstorms, and a surge through either the power supply or the field wiring can take out individual station outputs, the common circuit or the whole board.
• Dead backup battery. On older controllers a battery held the program through outages. When it dies the schedule is lost every time power blinks, which is why zones start running at odd hours.
• Failed station output. The switching component for one station fails. That station is dead or, less often, stuck on, while every other zone behaves normally.
• Corrosion in the terminal strip. Outdoor controllers in humid conditions corrode at the terminals until a wire loses contact.
• Programming error. Multiple overlapping programs, a stacked start time, a seasonal adjust left at an extreme, or a rain delay still active. Not a fault at all, and one of the more common reasons for a call.
• The fault is not the controller. A cut field wire, a dead solenoid or a failed valve produces symptoms identical to a controller problem. This is the most common misdiagnosis in irrigation.

How a technician diagnoses it

• We work from the wall outward, in the order the electricity travels.
• First, incoming power. Is the outlet live, is the GFCI tripped, is the breaker on, is the controller switched on. Then transformer output: a multimeter across the 24 VAC terminals tells us whether the power supply is producing what the valves need. A dark display with no transformer output is a power-supply fault, not a controller fault, and on many models that is an inexpensive part.
• Next, station output. With the controller manually running a zone, we measure across that station terminal and the common terminal. Roughly 24 volts AC means the controller is doing its job and the problem is downstream — wiring, solenoid or valve. No voltage on one station while others are fine means a failed output. No voltage on any station with a healthy transformer points at the board or the common circuit.
• Then field resistance. With the power off, a resistance reading from each station wire to common tells us about the far end without leaving the controller. An open reading means a broken wire or dead solenoid. A very low reading means a short, which is what has been blowing the fuse. Testing every station this way frequently finds faults the homeowner had not noticed yet.
• Finally we read the program, because a surprising number of "broken controller" calls are a rain delay still active, a seasonal adjust at 10%, or two programs overlapping so zones appear to run at random.

What the repair involves

1. Verify incoming power. Outlet, GFCI, breaker and switch checked first. Free to rule out, embarrassing to skip.
2. Test the transformer. Measured 24 VAC output tells us whether to replace a power supply or look further in.
3. Test every station. All stations are measured, not just the one that prompted the call, so latent faults are found now.
4. Check field wiring for shorts. Resistance readings identify shorted solenoids and damaged wire before a new fuse or a new controller gets destroyed by the same fault.
5. Repair or replace. A transformer, fuse, battery or terminal strip is replaced where that solves it. A board with multiple dead stations or surge damage is replaced with a controller sized to the station count, plus spare capacity if zones may be added.
6. Transfer wiring properly. On a replacement, every field wire is labelled and terminated to match the original zone numbering, so zone 3 is still the zone you think it is.
7. Program for the season and soil. Schedules are set inside the Georgia 4 p.m. to 10 a.m. landscape watering window, with cycle-and-soak run times suited to clay soil.
8. Run and hand over. Every zone is cycled, the program is walked through with you, and the zone-to-area map is written down.

What affects the cost

Controller work spans a wide range because it covers everything from a $6 fuse to a full replacement and rewire.

• Whether the fix is a fuse, battery, transformer, terminal strip or the whole controller
• Station count — a 6-zone controller costs considerably less than a 16-zone one
• Brand and model, and whether replacement parts are still manufactured for it
• Indoor versus outdoor enclosure, since weather-rated cabinets cost more
• Whether a smart or WiFi controller is being fitted instead of a conventional timer
• How much field wiring has to be traced, repaired or re-terminated
• Whether a short in the field has to be found before a new controller is safe to connect
• Whether surge protection or a new dedicated outlet is needed

For published rates and general North Georgia market ranges by repair type, see the Georgia irrigation repair cost guide.

Does this repair require digging?

Controller work itself involves no digging. The controller is mounted on a wall in a garage, basement, utility room or on an exterior wall, and all the work happens at the unit.

Digging only enters the picture when testing shows the fault is not the controller at all but a break in the buried field wiring, or a solenoid that needs replacing at a valve box. That becomes irrigation electrical repair or valve repair, and we will tell you which before any turf is cut.

How long does it take?

Diagnosing a controller and testing every station is typically well inside the first hour. Replacing a fuse, battery or transformer is quick once diagnosed. A full controller replacement takes longer because every field wire is labelled, transferred and terminated, then all programs are rebuilt and every zone run — usually a one-to-two hour job on a typical residential system.

Smart controller installations run longer than a like-for-like swap because of network setup, zone configuration and walking you through the app.

Should the water be shut off?

For most controller faults, setting the controller to OFF is enough — the valves stay closed and nothing runs.

The exception is a station stuck on. If a zone keeps running with the controller off or unplugged, the valve itself is passing water and the irrigation isolation valve needs closing. Unplugging a controller that is stuck on will not stop water if the valve has failed open mechanically.

If the controller is repeatedly blowing fuses, leave it off. There is a short in the field wiring, and repeatedly resetting it risks further damage to the board.

Will leaving it alone raise the water bill?

Controller faults drive up water bills quietly and often dramatically, because the failure mode is usually "waters more" rather than "stops watering".

A lost program reverting to factory defaults can put every zone on a daily schedule. Overlapping programs stack start times so the system runs two or three full cycles in a night. A dead rain sensor circuit means the system waters straight through a week of Georgia thunderstorms. A stuck station runs a zone continuously. In every case the system looks like it is working, so nobody investigates until the bill arrives.

This is the main practical argument for a smart controller: it adjusts to local weather automatically and flags unusual behaviour rather than silently repeating a bad schedule.

North Georgia considerations

Summer thunderstorms are the defining local factor. Frequent lightning across North Georgia means surge damage is a genuinely common cause of controller failure here, and it arrives through the field wiring as often as through the power supply — long buried wire runs make an effective antenna. Surge protection at the controller and a properly bonded common are worth the small extra cost.

Programming matters as much as hardware. The Georgia Water Stewardship Act restricts landscape watering with publicly supplied water to between 4 p.m. and 10 a.m. on any day of the week; watering between 10 a.m. and 4 p.m. is not permitted. Private wells and reuse water are exempt. Every controller we program is set inside that window, and start times are staggered so a multi-zone system finishes before the morning cutoff rather than being interrupted by it.

Clay soil shapes the schedule too. A single long run time on Piedmont clay runs off before it soaks in, so we program repeated shorter cycles with soak periods between them. That one change often fixes dry patches people had been blaming on the heads.

Frequently asked questions

Related services

Where we do this work

Irrigation Medics covers Hall County and the Lake Lanier communities, the Gwinnett corridor through Duluth, Suwanee and Buford, and North Fulton and Forsyth. Rates are the same everywhere — see the full service area.