PREVOST X3-45 Multiplex, Maintenance Manual

Page: 178 / 1422

Section 06: ELECTRICAL
PA1562
42
CAUTION
Never connect a voltmeter or V.O.M. to
measure bulb voltage as instrument will be
destroyed.
Troubleshooting and Safety
When switching on the Xenon headlamp using
the rocker switch, a lamp short-circuit test is
performed.
Current is detected in the lamp circuit before the
ignition time and ignition prevented. Connection
of the "hot" lamp to the body mass also prevents
ignition. In both cases, the system is cut off
within < 0.2 s and can only be restarted via the
rocker switch.
In general, the maximum ignition time is < 0.2 s,
which period is followed by cutoff. This would
happen if a lamp was defected.
Lamp missing: system is cut off after < 0.2 s.
If lamp components or cables are damaged by
force (accident) so that contact with hazardous
parts is possible, the current in these lines is
earthed by the vehicle body and - as with a
defective household appliance - switched off
when 30 mA are reached within < 0.2 s. the
cutoff time is shortened by a more powerful
defect current.
To protect the ballast, a counter in the electronic
safety system ensures that a defective lamp can
only be switched off 7 times consecutively after
a successful ignition, after which the device is
cut off. This prevents flutter and flashing. This
counter is put out of action when the lamp cutoff
time repetition interval is longer than 1.3 s so
that temporary non-defect disturbances that
result in immediate invisible re-ignition do not
cause lamp cutoff.
A warning notice on the lamp plug makes you
aware of the fact that the lamp is operated in this
system on a higher voltage (you should
therefore switch off the lamp before working on
this part).
After taking out the lamp, the contact pins are in
a practically idle state (< 34 Volt) after < 0.5
seconds so that there is no immediate danger of
electric shock even if the warning is
disregarded.
With this safety concept there is no danger to
check the ballast with a new bulb. There is a
very high probability that the ballast is OK if the
ballast can ignite the bulb.
One simple test to check the ballast would be to
measure the Nominal current of 1.58 A after one
minute for the 24V ballast.
9.2 STOP, TAIL, DIRECTIONAL, BACK-UP,
AND HAZARD WARNING LIGHTS
A combination stoplight, taillight, directional
signal light and back-up light assembly is
mounted at the rear, on each side of the vehicle.
Furthermore, when braking, two center
stoplights (LED) and a cyclops light (LED) will
illuminate simultaneously with the stoplights on
the sides for increased safety. The L.H. and
R.H. side center stop lights are also used as
directional signal and marker lights.
The stop, tail, directional signal and back-up
lights consist of individual LED lights mounted
on the engine rear door, and each light is
serviced individually as a complete unit. The
back-up light uses a regular tungsten bulb.
The hazard warning flashing system uses the
front, side and rear directional lights
simultaneously. This system is energized by a
switch on the L.H. dashboard.
9.2.1 Lamp Removal and Replacement
1. Open engine compartment rear door.
2. Remove the lamp support retaining screws
(2), and then from the outside, remove the
lamp and its support.
3. From the outside, install the new lamp with
its support then fasten the retaining screws.
9.2.2 Center Stoplights and Cyclops Light
Removal and Replacement
These (LED) lights are sealed unit and should
be replaced as an assembly in accordance with
the following procedure:
1. Unscrew both “Phillips” light screws then
remove the light assembly.
2. Install new light assembly and secure using
screws.
9.3 LICENSE PLATE LIGHT
Two LED units are mounted above the rear
license plate(s) of vehicle. In case of burn out,
the LED unit must be changed according to the
following procedure.