GMC 4000 Series Service Manual page 542

from flasher unit through switch, then to right-
hand signal. The same procedure applies to the
left-hand signal, except that lever is in the down
position and a different set of contacts are engaged
in switch assembly.
On conventional cab models, an arrow at either
side or tell-tale cluster flashes when either the
left or right signal light is illuminated. When turn
is completed, switch lever is automatically return­
ed to "OFF" position by a canceling cam installed
on steering wheel.
On tilt cab models, a tell-tale light on instru­
ment panel marked "TURN-SIG" flashes when either
the left or right signal light is illuminated. When
turn is completed, switch lever is automatically
returned to "OFF" position by a cancelling cam
installed on steering wheel.
If directional tell-tale on instrument panel
flashes in one position but not the other, check for
the following:
1. Directional lamp bulb burned out.
2. Incorrect directional lamp bulb installed.
3. Defective ground between bulb socket and
mounting.
4. Defective directional control switch a s­
sembly.
If directional tell-tale on instrument panel
does not flash in either direction, check for the
following:
1. Burned out fuse on fuse block.
2. Defective flasher or flasher terminals not
properly engaged in junction block.
3. Directional tell-tale bulb on instrument
panel burned out.
4. Short or open circuit. Check indicator lamp
circuit referring to wiring diagram in applicable
"Wiring Diagrams" booklet.
5. Defective directional control switch a s­
sembly.
If directional tell-tale light does not cancel
after completing a turn, remove the steering wheel
as explained in "MECHANICAL STEERING" (SEC.
9A) and check for a worn or damaged cancelling
cam.
MARKER BULB REPLACEMENT (Fig. 18)
Remove two screw s which retain amber mark­
er lens to light assembly, then detach lens. To re­
move bulb, press inward on bulb and turn counter­
clockwise to release from socket. Reverse above
procedure to install bulb.
DIRECTIONAL SIGNAL BULB
REPLACEMENT (Fig. 19)
Remove three screw s which retain circular
directional signal lens to light assembly, then de­
tach lens. To remove bulb, p ress inward on bulb
and turn counterclockwise to release from socket.
Reverse above procedure to install bulb.
G M C S E R V I C E M A N U A L ______________________
CHASSIS ELECTRICAL A N D INSTRUMENTS
contact, wiring and bearing assembly and a can­
celling cam (fig. 20). The control assem bly is in­
stalled over the steering shaft, inside the housing
and the cancelling cam is attached to the steering
wheel hub.
warning system , an additional switch is mounted
on side of the directional signal control housing
as shown in figure 21, except on tilt cab models.
REMOVAL (Fig. 20 or 21)
"Steering Wheel Replacement" in "MECHANICAL
STEERING" (SEC. 9A) of this manual.
panel harness connector.
CONTROL
CONTROL TO H O U SIN G
Figure 19— Directional Signal Light (Typical)
DIRECTIONAL SIGNAL CONTROL
ASSEMBLY
The control assem bly consists of a switch,
NOTE: On vehicles equipped with the hazard
1. Remove the steering wheel as directed in
2. Remove steering shaft upper bearing sleeve.
3. Disconnect wiring harness at instrument
NOTE: On some models it may be necessary
LEVER
I
SCREW (1 S H O W N )
Figure 2 0 — Directional Signal Control A ssem b ly
Page%3i
CONTROL
HORN R IN G A N D
BEARING ASSEMBLY