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Fixing a Wire Fault in a Two-Wire Decoder System


Streamline irrigation fault finding and wire repairs with the right approach to your system.

December 27, 2023

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Dealing with irrigation system faults doesn’t have to be a big, time-consuming problem. With proper irrigation wire path troubleshooting techniques, and an understanding of a two-wire system, you can quickly locate and repair a wire fault.


Tools needed for fixing a field wire fault

Having the right tools to address a wire fault repair can save you a lot of time. An issue that may take over a day to repair can get done in just hours when you’re properly prepared. A few essential tools include:

The clamp meter almost always means you won’t have to cut any wires to find faults. This can help make repairs easier.


Where to start diagnosing wire faults

Your irrigation system won’t keep quiet if something isn’t working properly. Signs that there’s a malfunction somewhere along the wire path are easy to see. Whether a component stops working altogether, if you suspect field wiring faults, it’s best to test all wiring to the decoders, using your clamp meter, to pinpoint your problem.

To do this, look at all major junctions within the branches of the irrigation system first to determine which branch has a short. Make sure you’ve verified all wiring requirements and system specifications with the manufacturer first so you have a baseline. You’ll see issues on your clamp meter as a higher-than-expected current reading. Next, use a halving procedure to pinpoint the exact location. The halving procedure minimizes the total number of measurements you’ll need to find the fault since, by testing the wire halfway down the line, you’ll be able to narrow down what section is faulty. Keep dividing the wire by half to get an exact location.

Consider making a rough sketch of the cables and decoder locations as you go to track your data and maintain a record of current readings.

Once you’ve found the location of the fault, you’ll be able to diagnose the issue, whether it’s a short circuit or an open circuit fault within the two-wire path or a solenoid.


How to fix irrigation wiring 

Once you’ve found the fault, the first thing to assess is whether there is earth leakage. This occurs when a cable or joint no longer has enough insulation to keep electricity from leaking into the ground. Repairs like these must be completed first since having this type of leakage can interfere with your ability to track and diagnose other faults. Earth leakages can also cause problems for some systems, leading to erratic operation or lack of use at all.

Once you’ve repaired any earth leakage, other field wiring faults can be addressed. If the system has a loop, you’ll want to break the loop at the fault point. This will give you a good half of the wire, that reads at nearly full volts, and a bad side, with a much lower reading.

To repair, you’ll add a wire splice, and while the most important thing is to ensure your repaired wire stays dry, the equipment you use can differ based on where your irrigation system fault is located.

For wires that aren’t buried directly in the ground, you can use a grease-filled wire nut to cap your spliced wires together. Make sure you don’t strip your wires too far down. The exposed wire must be shorter than the nut.

Twist your two ends together and screw on the grease-filled wire nuts to give the splice a solid, protective barrier against the elements.

For wires that are going back into the dirt, you’ll need to do a direct burial splice. This splice uses a regular wire nut, but the nut and wires go into a grease-filled tube to get that protective cover in place. The tube seals shut so the wires are kept dry.

No matter what splice you need to do, it’s also a good idea to bind your wires together in a secondary location. Using duct tape or waterproof tape, connect the wires together a little below the splice so there’s no risk they’ll separate if tugged on for any reason. 


Keeping irrigation systems working properly

Addressing issues related to irrigation wire faults means using your tools on the wire path and searching for the root of the problem. Once found, repairs to keep your irrigation system working properly aren’t too difficult. Should you, at any point, need assistance, stop in and talk to a local SiteOne branch associate. We can answer your questions and help ensure you have the right tools. You can also shop online at SiteOne.com or through our mobile app to ensure you’re fully prepared for any irrigation fault finding work.

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