Finding A Break In The Boundary Wire - Husqvarna Automower 420 Technical Manual

6.5 Finding a break in the boundary
wire
A break in the loop wire is normally due to inadvertent
physical damage to the wire, e.g. using a spade while
gardening. In countries with ground frost, sharp stones
that move in the ground can also damage the wire.
Breaks can also be due to high tension in the wire dur-
ing installation.
Mowing the grass too short right after the installa-
tion can damage cable insulation. Certain damage to
the insulation may not cause disruptions until several
weeks or months later. To avoid this, always select the
maximum cutting height the first week after installation
and then lower the height 1-2 steps at a time every
week until the desired cutting height has been reached.
A wire break can be found by using Husqvarna's break
detection tool or with the manual method that is de-
scribed below. A description of how the break detection
tool is used is available in a separate service bulletin.
There is a description below of how to search for
breaks without access to the break detection tool.
The procedure involves gradually halving the distance
of the loop where the break may have occurred until
there is only a very short section of the wire left.
1. Check that the LED in the charging station
flashes blue, which indicates a break in the
boundary wire. See 6.4 Troubleshooting the
loop signal on page 95 for more information
on charging station LEDs.
2. Check that the boundary wire connections to
the charging station are properly connected
and not damaged.
3. Disconnect all connections from the charging
station and then measure the resistance in the
boundary wire. A value over 20 Ohm indicates
that there is a break. If the measured value
is less than 20 Ohm and the LED still flashes
blues, the fault is in the charging station's
cabling or the circuit board. See
5.25 Replacing the circuit board, charging
station on page 78.
4. Connect the charging station to the power
supply. Switch the connections between
the guide wire and the boundary wire in the
charging station.
a) Switch connections AL and Guide. Check if
the LED is flashing yellow.
b) Put AL and Guide back in their original
positions. Then switch AR and Guide. Check if
the LED is flashing yellow.
If the LED is flashing yellow (i.e. the
boundary wire is intact but the guide wire
is not connected) in test a) then the break
6. TROUBLESHOOTING
A
AL
AL
Guide1
Guide1
AR
AR
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