Chevrolet Light Duty Truck 1973 Service Manual page 38

BLOW ER M OTO R IN O P E R A T IV E
(A N Y SPEED)
Check fuse
in fuse panel.
X
FUSE BLOW N
I
W ith Ig n itio n sw itch in
" R U N " p o s itio n and blow er
speed sw itch " O N " use
meter to locate sh o rt in one
o f the fo llo w in g w ires:
1. From fuse panel to blow er
speed sw itch .
2. From b lo w e r speed sw itch
to heater resistor.
POOR OR NO G RO UND
~ ' I
3. From heater resistor to
blow er.
Repair ground
N ote: S h o rt c ir c u it m ay be
in te rm itte n t. If m eter does
n o t in dicate a short c irc u it,
move harness around as
LA M P LIG H TS
I
m uch as possible to re-create
short c irc u it. W atch and
Replace M otor
listen fo r arcing.
L A M P DOES NO T L IG H T
Use 12 v o lt test lig h t and check feed
te rm in a l (b ro w n ) on blow er speed switch.
L A M P DOES NO T L IG H T
Repair open in b ro w n w ire
fro m b low er speed sw itch
to fuse panel.
H E A T E R C I R C U I T D I A G N O S I S *
FUSE OK
' 1
The fo llo w in g tests should be made w ith
the ig n itio n switch in " R U N " po sitio n
the blow er speed sw itch " O N " and the
lever on heat position.
I
Check blower m o to r ground
1
T
G R O U N D OK
Check m o to r conn ector
w ith 12 v o lt test lig h t.
L A M P DOES NO T L IG H T
I
Check blower feed wire in connector
on resistor with 12 volt test light.
L A M P L IG H T S
Repair open in feed wire
from resistor to blower motor.
L A M P L IG H T S
Replace sw itch
Fig. 1 3 -Heater Circuit Diagnosis
* See heater c irc u it diagrams