GMC 1982 Light Duty Truck Service Manual page 31

BLOWER MOTOR INOPERATIVE
(ANY SPEED)
Check fuse
in fuse panel.
FUSE BLOWN
T
With Ignition switch in
"R U N " position and blower
speed switch "O N " use
meter to locate short in one
of the following wires:
1. From fuse panel to blower
speed switch.
2. From blower speed switch
X
to heater resistor.
POOR OR NO GROUND
3. From heater resistor to
X
blower.
Repair ground
Note: Short circuit may be
intermittent. If meter does
not indicate a short circuit,
move harness around as
LAMP LIGHTS
much as possible to re-create
—
. 1
short circuit. Watch and
Replace Motor
listen for arcing.
LAMP DOES NOT LIGHT
X
Use 12 volt test light and check feed
terminal (brown) on blower speed switch.
LAMP DOES NOT LIGHT
Repair open in brown wire
from blower speed switch
to fuse panel.
HEATER C I R C U I T D I A G N O S I S *
FUSE OK
~ ' I-----
The following tests should be made with
the ignition switch in "R U N " position
the blower speed switch "O N" and the
lever on heat position.
I
Check blower motor ground
I
GROUND OK
X
Check motor connector
with 12 volt test light.
1
LAMP DOES NOT LIGHT
I
Check blower feed wire in connector
on resistor with 12 volt test light.
LAMP LIGHTS
Repair open in feed wire
from resistor to blower motor.
LAMP LIGHTS
Replace switch
' See heater c irc u it diagrams