G-Van Fuse Block; Power Door Lock System; Power Window System; Windshield Wiper - R/V And G-Van Models - GMC G Service Manual

8A-24 CAB ELECTRICAL
The other branch, coming out of the roof frame connec­
tor, goes back along the left roof halo panel, across the rear
halo panel and terminates at the rear door ground switch.
Also coming from this connector is a branch that goes down
the left front door lock frame to the left stepwell lamp
assembly.

G-VAN FUSE BLOCK

The fuse block holds the fuses and circuit breakers that
protect the circuits. The fuse block is located on the left side
of the dash panel and is fastened to the dash panel connec­
tor block with two screws. The fuse block connects to the
engine compartment harness. Power leads from the var­
ious circuits plug into the fuse block.
The fuses are encased in plastic and have twin blade
connectors. The fuses are printed and color coded with the
amperage rating. Refer to Figure 28.
□ □ □ □
□ □
WDO
□ □
IGN
[X]
K]
l
GAGES
2 0 A
TAIL LPS TURN/BU
DS
o
(I
C = 3
Figure 28 — Van Fuse Block

POWER DOOR LOCK SYSTEM

Individual motors operate each door lock. The direction
the motor turns depends on the polarity of the supply volt­
age. The door lock switches control the supply voltage
polarity. Each switch will lock all the doors.
Each motor has a self-resetting circuit breaker built in.
Voltage is present at the door lock switches at all times.
Voltage is also present on the open contacts of the door
lock relay at all times.
When a door switch is moved to "Lock," current flows
through the switch and lock relay coil to ground. The relay
closes, causing current to flow through the lock relay con­
tacts, door lock motor, the unlock relay contacts, and then
to ground.
□
c t x h e a t
□
□ □ □
□ □ □
ACC LPS PWR
INST LPS
r s n
AUX HTR A/C
K ]
HTR A/C
30A
PWR WOO
FUS PLR
L00247
When a door lock switch is moved to "Unlock," current
flows through the switch, the unlock relay contacts, the door
lock motor, the lock relay contacts, and to ground. This
causes the lock motor to unlock the door.
For R/V models, the door lock relay is located on the
dash panel, above the steering column. For G-Van models
the door lock relay is located on front left door hinge pillar.
For diagnosis, refer to "Diagnosis of Power Door Lock
System," later in this section.

POWER WINDOW SYSTEM

Each power window is moved by a single permanent
magnet motor. The direction the motor turns depends on
the polarity of the supply voltage. The control switches con­
trol the supply voltage polarity.
Switches for controlling all the power windows are
located at the driver's door. Each passenger window switch
controls only the window at that seating position.
The motors have a self resetting circuit breaker built in.
The circuit breaker allows the motor to be stalled without
damage. There are no travel-limit switches.
When a window switch is moved to "UP," current flows
through the circuit breaker, the window switch, the DK BLU
wire, the motor, the circuit breaker, the BRN wire, the "DN"
contacts in the switch, and into the BLK wire which goes to
ground.
For diagnosis, refer to "Diagnosis of Power Window Sys­
tem," later in this section.
WINDSHIELD WIPER — R/V AND
G-VAN MODELS
A permanent magnet type wiper is used on R/V and
G-Van Models. The motor parts-field magnets, armature,
drive gear, etc., are enclosed in a two piece sheet metal
housing. For purposes of explanation, the housing halves
are referred to as upper and lower housings. The two hous­
ings are attached to each other by ten extrusions which are
staked over.
The wiper motor is protected by an automatic reset type
circuit breaker located on the motor brush holder assembly.
A fuse located in the fuse block protects the vehicle wiring.
The wiper motor can be operated only when the ignition
switch is in the "run" or "accessory" position.
The wiper motor has three brushes; the "common," the
low speed, and the high speed. When the ignition switch is
"ON," power is applied to the common brush. The low
speed and high speed brushes are connected to their
respective ground via the control switch. When the control
switch is positioned at "HI" or "LO" speed, a ground path is
connected to the high or low speed brush in the motor. The
motor runs at the switch selected speed.
In order to have the wiper blades stop in their normal
park position and the wiper motor shut off properly, the
motor must run in LO speed. When the control switch is
moved to the OFF position, the low speed brush circuit
goes through a park switch located in the gear housing and
then to ground at the control switch. The park switch is
normally closed and this allows the wiper to keep running.
When the wiper blades reach their park position, cam on
the gear opens the normally closed park switch, which turns
off the wiper. Refer to Figures 29 and 30.
For wiper diagnosis, refer to "Diagnosis of Windshield
Wiper — R/V and G-Van," later in this section.