Windshield Wiper Delay Circuits; Heater System Circuits; Air Conditioning Electrical System - GMC G Service Manual

8A-26 CAB ELECTRICAL
WINDSHIELD WIPER
DELAY CIRCUIT
The wiper pulse control (delay) circuit is an option on
R/V and G-Van models. This option allows the wiper to
operate at a slower rate than the low speed setting on the
standard control.
The optional module is inserted into the harness under
the steering column (figure 32).
For delay circuit diagnosis, refer to "Diagnosis of the
Wiper Delay Circuit," in this section.

HEATER SYSTEM CIRCUITS

The heater blower motor is controlled by the blower
switch. The blower switch is a four position switch; off, low,
medium and high. This switch controls the speed of the
blower motor by connecting different resistances into the
motor circuit, thereby dropping the voltage available to the
motor.
The blower switch is located on the control assembly.
The harness from the switch goes to the dash panel con­
nector and into the engine compartment. The harness is
3. Ground— Park
4. Jumper— Park
17. Ground—High Speed
18. Ground— Low Speed
19. Power— Motor
F. High Speed Operation
G. Low Speed Operation
H. Park Operation
then routed to the resistor block, which is located on the
blower housing. From the resistor block, the harness then
goes to the blower motor. The wire colors can be found in
the wiring diagrams at the back of this manual.
For diagnosis and on-vehicle service of the heater
blower circuit, refer to HEATING AND VENTILATION
(SEC. 1A).
The compressor electro-magnetic clutch is turned on
and off by the pressure sensing switch. When the refriger­
ant pressure drops below a certain predetermined level, the
switch opens the compressor clutch circuit, which causes
the refrigeration system to stop working. The pressure
sensing switch is located near the top of the accumulator.
For diagnosis of the A/C electrical system, refer to AIR
CONDITIONING (SEC. 1B).
For air conditioning on-vehicle service, refer to AIR
CONDITIONING (SEC. 1B).
12V(
Figure 30 — Diagnosis Connection
AIR CONDITIONING
ELECTRICAL SYSTEM
17
F-00792