GMC 1982 Light Duty Truck Service Manual page 60

BLOWER MOTOR INOPERATIVE
(AN Y SPEED)
| ]
f u s e b l o w n
With ign. switch in "Run" position
and heater or A/C on, locate short in
one of the following wires: (see note)
1. From fuse panel to master
switch on control.
2. From master switch to compressor POOR OR NO GROUND
clutch.
3. Master switch to blower switch. Repair ground
4. From blower speed switch to
resistor.
5. From resistor to blower motor.
(LA M P L IG H T s l
Replace m otor
|LAMP L IG H T s l
NOTE: Short circuit may be inter­
mittent. If tester does not indicate
Repair open in
a short circuit, move heater harness
wire from blower
around as much as possible to re­
motor to blower
create short circuit. Watch and listen
relay.
for arcing.
| LAMP
Use 12 volt test light and check
wire terminals at resistor.
LAMP OFF
Check FEED wire from
resistor to blower
speed switch.
|LAMP | LAMP OFF
o n
X
Replace blower
Repair open in wire
speed switch.
from blower speed switch.
ELECTRICAL SYSTEM DI AGNOSTI C CHART
I USE |
f q k
The following tests should be made
w ith the ignition switch in "R u n "
position, heater or A/C on and
blower switch on high.
.............. r
Check blower m otor ground
T
X
I !
ground o k
Check motor connector with
12 volt test light.
|LA M P DOES NOT LIGH
t
Check wire connector on
blower relay with 12 volt test light.
1 LAMP DOES NOT L IG H t|
Check wire connector on blower
relay with 12 volt test light.
DOES NOT LIGHT!
I LAMP L IG H T s l
Replace relay
LAMP LIGHTS
Replace resistor
BLOWER MOTOR INOPERATIVE
(CERTAIN SPEEDS-EXCEPT HIGH
ON P-K FD IIR -'iFA 'inN l
Disconnect resistor connectors, connect one lead
of a self powered test light to any one terminal
and usa the other lead to probe each of the
other terminals.
TEST LIGHT DOES NOT
LIGHT ON ALL TERMINALS
I
Replace resistor
|
[LAMP LIGHTS IN ALL POSITIONS)
Connect 12 volt test light at wire
terminal on blower relay (wire
from resistor to blower relay).
|LA M P LIGHTS] I LAMP DOES NOT LIGH
X
Repair wire
Replace blower relay. Open in
from resistor to
blower relay.
TEST LIGHT LIGHTS ON
ALL TERMINALS
X
With ignition switch in "Run" position and heater
or A/C on, use 12 volt test lamp to check for
voltage at resistor connector with blower speed
switch in each position.
T
[LA M P DOES NOT LIGHT IN ALL PQSITIQNS|
Turn ignition key off and put Heater or A/C
Control in off position. With blower resistor wire
connector disconnected, connect a jumper lead
from battery positive terminal to the wire terminal
in connector. Use 12 volt test light to check for
voltage at wire at blower speed switch connector.
]
t
Repeat same test on the other wires.
LAMP LIGHTS ON LAMP DOES NOT LIGH T
ALL WIRES
ON ALL WIRES
Replace blower speed Repair open in
switch.
affected wire.