Troubleshooting irrigation controls

Too often, golf course irrigation system problems are not identified until it's too late. Suddenly, you're faced with a large area of stressed or burnt-out turf on your course and no way to bring it back to life. Even with the most advanced irrigation installations, there will be times where controllers, system wiring or valves will fail to operate according to the automated plan. Your sprinkler heads will sit there idle, waiting for instructions.

When an irrigation system goes on strike, the tendency is to look for a quick solution to bring the distressed areas back on line as soon as possible. Inexperienced technicians often focus their efforts on the most visible component in the system, the irrigation controller, placing the blame on a perceived problem within the complex electronics of the system's brain. It's a comforting thought that perhaps the irrigation can be revived by just changing out a few components within the controller, or the entire unit, as a way to quickly remedy the problem.

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However, this method is generally a waste of time. Even though expensive components may be changed out, the system will usually continue to misbehave after each attempt. And the technician will become more and more frustrated by this waste of time and efforts chasing an unidentified problem.

A better approach: Step-by-step troubleshooting

A better way to approach electrical system trouble shooting is with a step-by-step method that isolates and checks each of the irrigation components: the controller, the zone control valves and the wiring that connects it all together.

Step 1: Check the obvious.

Before launching a thorough system diagnosis, don't forget to check the obvious. Is the system water supply on? Are there isolation valves at the backflow preventer, pump station or in the mainline that are preventing water from flowing? Has the flow control on the valve been turned off? Has the “on/off/auto selector” on a valve-in-head sprinkler been left in the “off” position? Reviewing these factors up-front can save time and effort.

Step 2: Make sure you don't have a programming error.

If the zone operates fine manually using the controller's manual mode, but does not operate automatically, this usually indicates a programming error rather than an electrical problem. Review the controller's programming guide and look for data-entry mistakes.

Step 3: Know how to use a volt-ohm meter.

An inexpensive volt-ohm meter (VOM) will be your most valuable tool and a required component for successful electrical troubleshooting. VOMs can be purchased in the electrical-supplies section of a local hardware store, electronics shop (such as Radio Shack) or your local irrigation equipment supplier. Modern digital meters are more reliable and provide an easy-to read display that can give precise quantitative feedback of the system symptoms.

Step 4: Is the controller operational?

After these preliminary steps, you're now ready to check the controller itself. A blank LCD display or failure to respond to keyboard entries could indicate a lack of power to the unit or other damage. Begin by using your VOM to take a voltage reading of the primary incoming power to the controller. It should read somewhere between 110 to 125 volts. If it doesn't, you've found your problem. Unfortunately, it's seldom that easy.

In some cases, you'll notice that the display of the controller is scrambled, missing LED segments or the entire unit is “frozen” preventing buttons or dials from entering data. This is a symptom of “micro-processor lock-up,” where the primary brain of the controller has become confused with bad data from electrical surges or other causes. This can often be cleared by re-setting the device. Reset the controller by either disconnecting all electrical and battery power from the unit for several minutes, or by pressing a “reset” button which clears the memory of the processor and re-boots the system.

Step 5: Check for a tripped circuit breaker or blown fuse.

If the controller passes these tests, next check the station output of the controller to the valves that control the zones not receiving water. Again using the VOM, you can check to see if the output terminals indicate the 24 volts needed to open a standard solenoid. If you do not get a reading here, you should check for a blown fuse or tripped circuit breaker within the controller. Also check the output of the transformer in the controller to make sure that it is outputting correct voltage.

A blown fuse or tripped circuit breaker in most controllers indicates an overload condition in the field, not a problem with the controller. If one of these problems is present, you can certainly replace or reset the controller. However this will not solve the root cause of the problem with either the field wiring or valve solenoid.

If you are fortunate enough to have a top-of-the-line controller, you may have the benefit of a more modern feature called “automatic short-circuit detection” which is a specialized self-diagnostic system within the controller itself. This handy feature allows the controller to identify a zone that has a fault in the field wire or valve and skip over the affected zone, eliminating a blown fuse. The best part of this feature is that the controller will digitally display a message that says: “Station 3 Error” to assist with locating the valve or field wire problem.

Step 6: Check field wiring.

If the controller, transformer and station outputs all work properly, the next place to check is the field wiring. And this happens to be the most common place where unforeseen problems occur.

Use the VOM to perform an “ohm test” on a specific zone circuit (the common wire plus a station wire), with the controller power turned off. At this point, you will want to make sure the VOM is set to the correct resistance setting to make sure the unit provides accurate and measurable feedback. Make sure to disconnect the wires you are testing from the controller terminal block so that your reading is specific to the wires in the field and not mixed up with feedback through the circuits of the controller.

The “ohm test” will send a small pulse of current from the battery in the VOM through the circuit to measure resistance. A normal reading is 20 to 60 ohms.

If the circuit has a “short,” meaning the current is taking a shortcut back to the controller, the reading may be as low as 1 to 10 ohms. If the circuit is completely broken, you will get a reading of infinity, meaning there is no clear path for the electricity to flow back through the circuit and to the VOM (thus, resistance is total, or “infinite”).

A reading of a high number, but not infinity, would indicate that there is still an intact circuit, but there is a high amount of resistance in the circuit that is keeping current from flowing well enough to activate a solenoid valve. This is a common symptom of a bad electrical connection, often an underground splice that was not properly waterproofed.

Test each circuit from the controller and you'll notice a pattern. The good circuits will have similar readings and the bad circuit will stand out from the others. This gives you confidence in the process and helps you work specifically to the final step of checking the valve solenoid.

Step 7: Check the valve solenoid.

The final step in a systematic approach is to decide whether diagnosed problems in the field wiring are related to the wiring and splices, or to the specific solenoid on the valve, or the valve-in-head sprinkler. At this point, you'll move to the actual location of the valve in the field and cut into the wires leading into the solenoid to take an ohm reading of the solenoid's resistance. Typically, if the solenoid is bad, you will get a reading for a “short” or 1 to 10 ohms. (There is no need to test voltage at the valve because you have already “ohm tested” each circuit at the controller and you should know which zones have problems.)

Sharpen your troubleshooting skills

I've presented some basic steps in this article in simplified fashion. However, electrical troubleshooting an irrigation control system using a step-by-step process takes time to learn and requires a willingness to try multiple approaches before finding the solution to your problem. Many irrigation manufacturers and distributors offer training classes on electrical troubleshooting that will give you an opportunity to get hands-on experience with this process.

A few hours in an irrigation troubleshooting course can provide valuable training for that hot summer day when you face stressed turf and a system that will not operate.

Jeff Carowitz is vice president of marketing for Hunter Industries (San Marcos, Calif.).

Irrigation wiring diagram (highly simplified)

Steps for diagnosing irrigation electrical problems*

  • First, check primary power. Reading should be 110 to 120 volts.

  • Next, check power output from controller to solenoids by testing voltage at C1, C2 and C3. No voltage here probably indicates a blown fuse or tripped breaker in the controller.

  • Next, disconnect common and control wires from the controller and then test resistance through each circuit (C1 and common, C2 and common, etc.). If the resistance is high or infinite, you know you've got a break or a bad connection. Too low and you have a short.

  • If the previous test indicates a problem in a particular circuit, you should next test the solenoid (S1, S2 or S3) in that circuit. Cut into the solenoid wires (to bypass all splices in the circuit) and test resistance in the solenoid. An abnormal reading indicates that the solenoid is faulty.

* See table, facing page, for VOM values.

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