How to Find a Break in Robotic Mower Boundary Wire (No Loop Signal)

A broken boundary wire stops a wired robotic mower with a “no loop signal” error. On a Husqvarna Automower, the charging station light also flashes blue. Check the connectors at the charging station and any existing splices first. If they are fine, find the break by halving the loop with a spare length of wire, by tracing it with a wire break detector, or by testing sections with a multimeter, then join the ends with a waterproof coupler.

Last reviewed: October 2026. The steps come from Husqvarna’s US help center and Segway Navimow’s maintenance guide. Check your own mower’s manual, because connectors and indicator lights vary by brand.

Signs of a wire break

The mower or its app reports “no loop signal.”
On an Automower, the charging station indicator flashes blue instead of showing solid green.

Check these first

The boundary and guide wire connectors at the charging station: secure, dry, and undamaged.
Every existing splice in the loop. Make sure each coupler is intact. An installation map shows where the wire runs.
Any recent digging, edging, or planting along the wire. Navimow lists digging, roots, rodents, weather, aging, corrosion, and poor plug connections as common causes.

Method 1: halve the loop

This is Husqvarna’s manual search. It needs a spare length of boundary wire and connectors. On an Automower, turn ECO mode off first, because the search will not work with it on.

Disconnect the section you suspect from the charging station.
Connect one end of a new length of wire to the empty slot on the station.
Cut the suspect section at its midpoint, and connect the other end of the new wire to the half still attached to the station.
Check the indicator. If it turns solid green, the break is in the half you disconnected. If it keeps flashing, the break is in the other half.
Repeat, halving the section each time, until only a short piece is left. That piece contains the break.

Husqvarna also describes swapping the guide wire and boundary wire connections at the station to tell which of the two wires is broken. If the damaged stretch is short, replacing it entirely may be easier than finding the exact spot.

Method 2: trace it with a detector

A wire break detector, or signal locator, sends a signal through the wire and lets you follow it above ground with a handheld receiver. The break is near where the signal stops. Husqvarna says a detector finds clean breaks without cutting the wire but is less reliable for partial breaks. Navimow adds that a phone or radio can be used to listen for the signal, which is quicker but less accurate.

Method 3: test sections with a multimeter

Navimow’s guide suggests disconnecting both ends of the wire and measuring resistance in ohms. An infinite reading means the wire is broken, and a reading under 10 ohms means it is intact. Divide the wire into sections and test them one after another to narrow down the break.

Repair the break

Cut out the damaged section. Husqvarna suggests trimming about 2 feet on each side of it.
Push both wire ends into a waterproof coupler, one end per hole. Use the mower maker’s couplers where you can.
Check through the coupler’s clear side that both wires are fully seated, then press it shut with pliers.
Reconnect the station and confirm the loop signal before you cover anything.
Bury the wire and coupler, or pin them down with staples, so they are not damaged again. Navimow suggests re-laying wire about 3 to 5 cm, roughly 1 to 2 inches, deep.

Tools: spare boundary wire, couplers and connectors, pliers, and a wire cutter. A multimeter or wire break detector is optional.

If the signal still does not return

Husqvarna advises contacting a local dealer if the station still flashes blue after these steps. A dealer or installer can trace the loop and quote a repair. See robotic mower repair for other faults, who repairs home robots for the options, and the glossary for terms like loop signal and coupler.

Frequently asked questions

What causes a boundary wire break?

Navimow lists digging and spadework, roots, rodents, weather, and aging, corroded, or loose connections as the common causes.

Can I find a wire break with a radio?

Navimow’s guide says a phone or radio can be used to listen for signal loss along the wire, but it is less accurate than a multimeter or a dedicated locator.

Does a wire-free mower have this problem?

No. Wire-free mowers that use RTK satellite positioning or cameras have no boundary wire to break. See how robotic mower installation works for the difference.

Related guides

Sources

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