GMC 4000 Series Service Manual page 537

Sec. 12
Page 526
CHASSIS ELECTRICAL AND INSTRUMENTS
VERTICAL
ADJUSTING SCREWS
HORIZONTAL
ADJUSTING SCREW S 3 1
V IE W C
adjusted so the high intensity zone of the light beam
is just to the right of the headlight center and just
below the headlight level at 25 feet. To obtain cor­
rect adjustment, beam adjustment should be made
with the vehicle loaded with the normal average
load it will be carrying during the majority of its
operation. T ires should be uniformly inflated to
recommended pressure when adjusting headlight
beams. Beam adjusting screws are identified in
View A, figure 12, for dual units and in figure 13
for single units.
In all cases, it must be remembered that state
or local legislation and specific vehicle conditions
will govern the final aim for the best and safest
lighting. Especially in the case of vehicles carry­
ing widely varying loads during night-time oper­
ation, the final decision as to safe operation must
still be made on the basis of "the most light on the
road with the least annoyance to oncoming traffic."
DUAL SEALED BEAM UNIT REPLACEMENT
Removal (Fig. 12)
1. Using a hooked tool, disengage spring from
G M C S E R V I C E M A N U A L
gj||
RETAINING RING
ATTACHING SCREWS
Figure 12— D ual Sealed Beam Unit Replacement
headlamp retaining ring as shown in View "B."
engage mounting ring from horizontal and vertical
adjusting screw s, then pull the assembly forward
to remove (View B).
sealed beam unit.
to mounting ring. Separate retaining ring from
mounting ring and remove sealed beam unit and
discard (View D).
Installation (Fig. 12)
molded on top of lens must be used at inside light
position and unit with number "2" on lens must be
used at outside position.
then place retaining ring over sealed-beam unit
and attach to mounting ring (View D).
tion and p ress wiring connector plug onto terminals
on sealed-beam unit.
HOOKED TOOL
V IE W B
SEALED
RETAINING
BEAM UNIT
RING
V IE W D
2. Rotate the sealed beam unit slightly to dis­
3. Pull headlamp wiring connector off back of
4. Remove screw s which attach retaining ring
NOTE: Sealed-beam unit with number "1"
1. Position sealed-beam unit in mounting ring,
2. Move sealed-beam unit assembly into p osi­
rw ii— - - -------
RETAINING I
RING SPRING
HEADLAMP
M O U N T IN G RING
T -4429