Chevrolet 70 Series 1970, Service Manual

Page: 771 / 841

CHASSIS ELECTRICAL AND INSTRUMENTS 12-25
VERTICAL CENTERLINE
STRAIGHT AHEAD OF >
VERTICAL AIM * TOP EDGE OF
HIGH INTENSITY ZONE AT (H)*-
LIMITS H + 2 JN — _____
A HORIZONTAL CENTERLINE
J
LOCATED' AT LEVEL OF
LAMP CENTER 1 1
LATERAL AIM - LEFT EDGE
OF HIGH INTENSITY ZONE
J
2 IN. RIGHT OF (V) ....
L
LIMITS V TO A IN. RIGHT—
- A
--------------- — V i/
/
1
HIGH ^
At!*TENSITY ZON{/
AIM INSPECTION LIM ITS FOR LOWER BEAM OF:
534 in. T ype 2 Sealed Beam
7 in. T ype 2 Sealed Beam
Caution—Do not aim or inspect these lamps on the upper
beam
VERTICAL CENTERLINE
(
STRAIGHT AHEAD OF
VERTICAL AIM - HIGH
INTENSITY ZONE
CENTERED 2 IN. BELOW (H)-p\
LIMITS * 2 cenVjA
k HORIZON!
V
LOCATED
LAMP CEN
2 IN.—
HIC.H
AL CENTERLINE
AT LEVEL OF
TER—
-J
*
V INTENSI1
LATERAL AIM - HIGH j
INTENSITY ZONE
CENTERED ON
N \
—
7"5oF7E_y ~
1
1
1
-M
AIM INSPECTION LIM ITS FOR UPPER BEAM OF:
534 in. Type 1 Sealed Beam
7 in. Sealed Beam, except Type 2 T-3491
Figure 22—Visual Headlight Beam Adjustment ITypical)
sh eet m etal, the headlam ps m ust be checked for
proper aim .
In addition to providing su p erior lighting, the
"T-3" type sea led -b ea m unit p rem its adjustment
of the light without the u se of an aim ing sc r e e n
and without requiring a la r g e work area . A im ing is
accom p lish ed with the u se of a safety aim er (J-6878
-0 1 ). Instructions for u sin g the Safety A im er are
supplied by the instrum ent m anufacturer.
H orizontal and v e r tic a l aim ing of each se a le d -
beam unit is provided by two adjusting s c r e w s,
v is ib le through the b e z e l, which m ove the mounting
ring against tension of the co il spring.
Headlight beam adjustm ent requirem ents w ill
vary on different v e h ic le s due to s iz e and d istrib ­
ution of load, type of standard o r optional su sp en ­
sion , s iz e of tir e s , tir e p r e s s u r e s , and other fa c ­
to r s . A verage req u irem en ts a r e for the high in ten s­
ity zone of the high b eam s of inner ligh ts on dual
units to be straight ahead and
2
inches below the
headlight le v e l at 25 fe e t. Low beam of outer lights
of dual units and a ll 7 -in ch units should be adjusted
so the high intensity zone of the light beam is just
to the right of the headlight center and just below
the headlight le v e l at 25 feet (fig. 22).
To obtain co r r e ct adjustm ent, beam adjustment
should be made with the v eh icle loaded w ith the
norm al average load it w ill be carrying during the
m ajority of its operation. T ir e s should be uniform ­
ly inflated to reco m m en d ed p ressu re when adjusting
headlight b ea m s. B eam adjusting sc r e w s are iden­
tified in V iew A, figu re 23, fo r dual units and in
figu re 24 for sin g le u nits.
In a ll c a s e s , it m ust be rem em bered that sta te
o r lo ca l le g isla tio n and sp e c ific v eh icle conditions
w ill govern the final aim fo r the b est and s a fe s t
lighting. E sp ecia lly in the c a se of v e h ic le s c a r r y ­
ing w idely varying loads during night-tim e o p er­
ation, the final d ecision a s to sa fe operation m ust
s t ill be made on the b a sis of "the m ost light on the
road with the le a s t annoyance to oncom ing traffic."
DUAL SEALED-BEAM UNIT REPLACEMENT
R em oval (F ig. 23)
1. U sing a hooked to o l, disengage spring from
headlamp retaining ring a s shown in View B .
2. Rotate the se a le d beam unit sligh tly to d is ­
engage mounting ring from horizontal and v ertica l
adjusting sc r e w s , then pull the a ssem b ly forw ard
to rem ove (View B).
3. P u ll headlamp w iring connector off back of
se a le d beam unit.
4. R em ove sc r e w s which attach retaining ring
to mounting ring. Separate retaining ring from
m ounting. ring and rem ove se a le d beam unit and
d iscard (View D ).
Installation (F ig. 23)
* NOTE: Sealed -b eam unit with number "1”
m olded on top of le n s must be u sed at in sid e light
p osition and unit w ith number "
2
" on le n s m ust be
u sed at outside p osition .
1. P o sitio n se a led -b e a m unit in mounting ring,
then p la ce retaining ring over se a led -b ea m unit
and attach to mounting ring (View D ).
2. Move se a led -b ea m unit a ssem b ly into p o s i­
tion and p r e s s w iring connector plug onto term in a ls
on sea led -b ea m unit.
3. P r e s s in on the a ssem b ly and rotate sligh tly
to engage horizontal and v e r tic a l adjusting sc rew s
in slo t in headlamp mounting ring.
4. U sing the hooked to o l, pull outward on r e ­
taining ring spring and engage in slo t in retaining
ring a s shown in "View B."
5. Check headlight adjustm ent a s explained
under "Headlight B eam Adjustment" p rev io u sly .
SINGLE SEALED-BEAM
UNIT REPLACEMENT
R em oval (Fig. 24)
1. R em ove sc r e w s which attach headlamp
b e z e l to mounting ring, then rem ove the b ezel.
2. R em ove sc r e w s w hich attach headlamp r e ­
taining ring to mounting rin g. U sing a hooked tool,
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL