Irrigation controllers or irrigation clocks are sometimes referred to as the brains of the system. There are many types of irrigation controllers. Some are analog or mechanical but the vast majority are electronic. While the analog controllers have been the workhorse since the 1960s, the electronic controller has taken its place due to lower costs to build, compactness and flexibility. There are many types of electronic controllers available but the ones dealt with here are the residential and light commercial ones. Of these, the ones you will probably see will be either indoor mount or outdoor mount controllers. Indoor controllers are designed to be used indoors and are not enclosed in a weatherproof cabinet.  Indoor controllers attach to electrical outlets via a plug-in transformer. This transformer steps down your household voltage from 120VAC to 24VAC. Outdoor irrigation controllers are housed in a weatherproof cabinet and rated for outdoor use. Outdoor controllers have the transformer located inside the cabinet.  To hook up the controller, you must bring 120VAC into the cabinet and wire directly to the transformer. Once the electricity leaves the transformer, it has been stepped down from high voltage (120VAC) to low voltage (24VAC). The irrigation controller and the electronic solenoid valves are powered by the lower 24 VAC voltage.

The first step of troubleshooting an irrigation controller is to verify proper voltage before and after the transformer with a voltmeter. To do this, set your voltmeter to AC volts (the icon with the wavy line) and to a number greater than the voltages you are checking (for example, if you are checking for 120V, set your voltmeter to 200V; if you are checking for 24V set your meter to 50V. The reason for this is so you will get an accurate voltage reading.). On indoor controllers, this means verifying you have 120VAC at the outlet and then testing for 24VAC where the cord from the plug-in transformer connects to the irrigation controller. On outdoor controllers, you need to check for 120 VAC where the incoming power attaches to the transformer and then check for 24VAC coming out of the transformer.

If you have 120VAC being supplied to the transformer, but do not have a 24 VAC output, replace the transformer with a correct model replacement part. It should be noted that often power surges can short out transformers.  Before replacing the transformer, check to see if there is any indication of hot spots on the circuitry of the controller. By removing the face cover you should be able to identify any areas that may have been blackened by a surge. If the circuitry is damaged then replace the controller and transformer.

If the transformer checks out ok and there is still no power being supplied to the controller, check the fuse (if applicable) on the controller. To do this, set your volt/ohmmeter to Ohms (Ω) and the audible setting. When you touch the two ends of the fuse, you should hear a tone. If there is no tone, the fuse is bad. Some irrigation controllers are equipped with fast-blow fuses. Remove the fuse and check the thin filament. Always replace blown fuses with the same amperage fuse. Blown fuses are an indication of power surges that could also short electric valve solenoids in the field. Refer back to the valve troubleshooting section to learn how to identify shorted valve solenoids. 

Today’s electrical controllers rely on circuitry and microprocessors to send power to the electrical solenoid valves. If your digital irrigation controller begins to lock up or has errors in the programs, you may need to reset the microprocessor. To do this, remove all power from the controller. Disconnect the power supply and remove any backup batteries. Wait 5-15 minutes for the controller to power down and then replace backup batteries and restore power. Reprogram and then test controller.

Programming the Controller

To get the most out of an irrigation system the irrigation controller must be programmed properly. If you take just a moment to access what you will be watering the process will not be so daunting. Most of the controllers on the market these days come equipped with the items listed in the terminology section below. The exception to this is what we call “smart controllers”. Those units have the ability to be autonomous after installing the base information.

Most of us have landscaping that is functional and pleasing but not intricate in design or maintenance. Therefore keep the programming as simple as possible.  Most of us will not need to use all the programs and start times available on the controllers. The only times these extra’s may come into play is in the initial establishment of the landscape.

The basic program consists of inputting the date, the present time of day, and the year. After that select program “A”  and input the days of watering needed, the zone run times, and the start time(s). The irrigation frequency and run times are dependent on the climate, soils, and plant materials.


Programs- Most controllers come with at least 2 and up to 4 programs. Programs allow you to apply different watering schedules to various types of plant material that have non-similar watering requirements. For example, annual flowers planted in raised beds may need to be watered every day whereas grassed areas may only need to be watered 3 days a week. In this scenario, annual flowers may be on program A and lawn areas on program B. It is important to note that whenever information is entered into the controller under any of the various programs, each program will run concurrently regardless of the program positioning switch or screen display.

Cycles- The cycle section of the controller refers to the daily interval that the program will run. Most controllers give you 4 options on how you can run the daily intervals.

Odd- This setting runs the program every other day on the odd-numbered calendar days.    

Even- This setting runs the program every other day on the odd-numbered calendar days.

Custom- This lets you choose exactly which days of the week the program will run.

Cyclic- Allows watering at a preset interval.

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