Troubleshooting - Hilti DD 120 Operating Instructions Manual

use a spray, pressure jet washer or running water for
cleaning. This may negatively affect the electrical safety
of the machine.
8.3 Maintenance
WARNING
Repairs to the electrical section of the machine may
be carried out only by trained electrical specialists.
Check all external parts of the power tool for damage
at regular intervals and check that all controls operate
faultlessly. Do not operate the power tool if parts are
damaged or when the controls do not function faultlessly.
If necessary, the power tool should be repaired by Hilti
Service.
8.4 Replacing carbon brushes 10
NOTE
The indicator lamp with the wrench symbol lights up
when the carbon brushes need to be replaced.
DANGER
The machine may be operated, serviced and repaired
only by trained, authorized personnel. This personnel
must be particularly informed of any possible hazards.
Failure to observe the following instructions may result in
contact with dangerous electric voltage.

9 Troubleshooting

Fault
The machine doesn't start.
1.
2.
3.
4.
5.
8.5 Adjusting the play between rail and carriage
NOTE
Play between the rail and the carriage can be adjusted
by turning the carriage play adjustment screws.
Use an Allen key to tighten the carriage adjustment
screws to a torque of 5 Nm (finger-tight) and then turn
the screws back ¹/₄ of a turn.
The carriage is correctly adjusted if it remains in position
when no core bit is fitted but moves down under its own
weight when a core bit is fitted.
8.6 Checking the power tool after care and
After carrying out care and maintenance, check that all
protective and safety devices are fitted and that they
function faultlessly.
Possible cause
Interruption in the electric supply.
On/off switch defective.
Interruption in the electric supply.
The electronics are defective.
Water in the machine.
Disconnect the machine from the electric supply.
Open the carbon brush covers on the left-hand and
right-hand side of the motor.
Take note of how the carbon brushes are fitted and
how the conductors are positioned. Remove the
worn carbon brushes from the machine.
Fit the new carbon brushes just as the old ones were
fitted (spare part number: 39577 carbon brushes
AO ML 100‑120 V: 209487/209488; 39576 carbon
brushes AO ML 220‑240 V: 209485/209486).
NOTE Take care to avoid damaging the insulation
on the indicator lead as you insert the brushes.
Close the carbon brush covers on the left-hand and
right-hand side of the motor and tighten the retaining
screws.
NOTE The indicator lamp goes out after the carbon
brushes have been replaced.
maintenance
Remedy
Plug in another electric appliance and
check whether it works. Check the
plug connections, supply cords and
extension cords, PRCD and electric
supply.
If necessary, the power tool should be
repaired by Hilti Service.
Check the supply cord, extension
cord, supply cord plug, PRCD and
have them replaced by a qualified
electrician if necessary.
The machine should be repaired by
Hilti Service.
Dry the machine.
The machine should be repaired by
Hilti Service.
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