Aiming Headlamps; Headlamps Adjustment - PREVOST H3-41 Maintenance Manual

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 30mA 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 stat (< 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 1.58A after one
minute for the 24V ballast.

16.2.5 Aiming headlamps

Headlamps must be properly aimed to provide
maximum allowable road illumination. Aiming
can be performed without opening headlamps
assembly. Vertical aiming of each module is
provided by one adjusting screw that pivots the
entire module in the housing for proper
alignment (
FIGURE 85
focus since the module is set for proper focus
during manufacturing assembly.
FIGURE 84: HEADLAMPS ASSEMBLY
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FIGURE 85: VERTICAL AIMING

16.3 HEADLAMPS ADJUSTMENT

1. Headlamp aiming and inspection can be
accomplished by visual means. This is done
on a screen located at a distance of 25 feet
(7,6 m) of the headlamps. It should be of
adequate size with a matte-white surface
well shaded from extraneous light and
properly adjusted to the floor area on which
the vehicle stands. Provisions should be
made for moving the screen or its vertical
centerline so that it can be aligned with the
vehicle axis. In addition to the vertical
centerline, the screen should be provided
with four laterally adjustable vertical tapes
and two vertically adjustable horizontal
tapes.
PA1621 Maintenance Manual All Series | Revised Sept 2019
SECTION 06: ELECTRICAL
). There is no adjustment for
85
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