Husqvarna Automower 420 Technical Manual page 92

The robotic lawnmower
travels in a small circle or
one wheel locks up when
turning instead of rotating
backwards.
The robotic lawnmower
does not react when
pressing the STOP button
The robotic lawnmower
does not react when the
cover is closed.
6.2.2 Symptoms when searching
Table 6: Symptoms during searching
Symptom
The robotic lawnmower
runs, but the blade disc
does not rotate
The robotic lawnmower
does not run along
the guide wire when
it is searching for the
charging station.
English - 92
6. TROUBLESHOOTING
The wheel motor's gearbox is
slipping.
Faulty microswitch.
See above.
Cause
The robotic lawnmower is
searching for the charging
station. The blade disc does
not rotate when the mower
is searching for the charging
station.
The guide loop is broken.
Check the wheel motor function when idling
via the Tools menu or use Autocheck EXP.
The battery voltage should be more than
18 V in this test. Check that both wheel
motors start with 50% power. Then increase
the power to 100%. At 100% the speed
of each wheel should be at least 35 cm/
second. Check that the motors' gearboxes
are not slipping by blocking each wheel. In
connection with blocking, the speed should
be 0 cm/second. Replace the wheel motor if
there is a fault.
Check and replace if necessary the STOP
button's microswitch.
See above.
Action
This behavior is normal and no action is
required.
Refer to 6.4 Troubleshooting the loop signal
on page 95.