Robot Mower Boundary Wire Break: Find and Fix It

On this page4 sections

1. Why this happens
2. Fix it in order
3. Common causes and prevention
4. When it is the robot, not your lawn

What is going wrong

• 1The containment fieldThe loop does not fence the mower in physically. It radiates a signal the machine reads as the edge, so the working area exists only while current runs the whole way round.
• 2The breakCopper can be severed inside insulation that still looks perfect from above, so the fault is usually invisible until you cut in.
• 3Dock terminalsA loose or oxidized terminal produces the same fault as a cut wire, and is the only join you can check without digging.

Why this happens

On boundary-wire models, a continuous loop of wire carries a low signal that the mower reads to stay inside your yard. The loop has to be electrically complete for that signal to exist. When the wire is cut or its copper core snaps, the signal stops and the machine refuses to work, since it can no longer tell where the edge is. A break can look like nothing at all from above, because the insulation may be intact while the copper inside is severed. Wire-free GPS or RTK models do not use a perimeter loop, so this fault does not apply to them.

Fix it in order

Work through these from the top. Note the fault the dock or app reports before you start.

1. 1

   Terminals seated

   Check the connections at the dock.

   Confirm both ends of the loop are seated in their terminals and free of corrosion. A loose or oxidized terminal mimics a break and is the easiest thing to rule out.

2. 2

   Loop walked

   Walk the whole loop.

   Follow the wire and look for spade cuts, aeration marks, edging damage, animal chewing, and spots pulled up above ground. Recent yard work is a frequent cause.

3. 3

   Pinch points

   Inspect the pinch points.

   Look hardest where the wire crosses paths, passes staples, or was buried shallow. These take the most stress and fail first.

4. 4

   Half ruled out

   Use a halving search.

   If the break is not visible, split the loop. Reconnect one half directly at the dock to form a shorter test loop and see whether the fault clears. Whichever half still faults contains the break. Halve that section again, and repeat until you have narrowed it to a short run you can dig up and examine.

5. 5

   Spliced

   Cut in and splice.

   Once you find the break, cut back to clean copper on both sides and rejoin them with a waterproof gel-filled connector made for buried low-voltage wire. A twist of bare wire or household tape will corrode and fail again.

6. 6

   Loop restored

   Restore and test.

   Rebury the repaired section, reconnect the full loop at the dock, confirm the fault has cleared, and run a short supervised cycle.

Common causes and prevention

• Yard tools. Spades, edgers, and aerators cut shallow wire. Mark the loop path before you dig.
• Freeze and thaw. Ground movement over winter can stretch and snap a shallow or taut wire. Leave a little slack when you lay it.
• Poor original splices. Earlier repairs made with tape or non-sealed connectors corrode. Redo them with gel connectors while you are there.
• Animals and mowers. Chewing and a conventional mower running over an exposed section both cut the wire. Keep it buried or stapled flat.