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Automower error E02 “No loop signal” — how to find the real cause

Error 02 means the mower can't detect the signal that the charging station drives through your boundary wire. Most advice jumps straight to “your wire is cut” — but the single most useful diagnostic fact is where the error happens:

• E02 only at or near the charging station, mowing runs are clean → the problem is the station side: its power supply, the low-voltage cable, corroded loop-wire terminals (AL/AR), or the station board. The wire in your lawn is fine.
• E02 out in the lawn → suspect the boundary wire: a cut (aerators, edging tools, animals) or a corroded joint.

If it happens at the station

1. Watch the station LED during an episode. Steady green: signal fine, look at contacts. Flashing blue: the loop signal itself is dropping — power supply or connections. Cycling green→red→off→green: the station is rebooting, classic failing power supply.
2. A failing switch-mode power supply can read a normal voltage (~28 V) with a multimeter when idle, yet collapse under charging load — “hiccup mode”. If problems start 10–20 minutes into a charge, that's the signature.
3. Check the low-voltage cable end to end for damage, and unclip/re-strip the AL/AR loop terminals at the station.
4. The power supply is the cheapest and most common fix; the station circuit board is the suspect only if a known-good supply doesn't cure it.

If it happens in the lawn

1. The station LED will flash blue with a broken loop.
2. Walk the wire route for visible damage; check every joint — twisted-and-taped joints corrode, use gel-filled connectors.
3. An AM radio tuned off-station held near the wire (or a dealer's loop tester) locates the break.