Chevrolet Light Duty Truck 1973 Service Manual page 109

B LO W E R M O T O R IN O P E R A T IV E
(A N Y S P E E D )
Check fo r proper
fuse
|F U S E B L O W N !
W ith ign. switch in " R u n " position
and heater or A /C on, locate short in
one of the fo llo w in g wires: (see note)
C-K Four-Season System
1. From fuse panel to master
switch on control.
2. From master switch to compressor |P O O R OR NO G R 0 U N D |
clutch.
3. Master sw itch to blower switch. I Repair g ro u n d |
4. From blow er speed switch to
resistor.
5. From resistor to blow er m otor.
| LA M P L IG H T S ]
Except C-K Four-Season
Replace m o to r
1. From fuse panel to blower switch.
2. From blow er switch to resistor.
3. From resistor to blow er m otor.
|L A M P L IG H T S !
NOTE: S h ort c irc u it may be in te r­
m itte n t. If tester does not indicate
R epair o pe n in
a short c irc u it, move heater harness
w ire fro m b lo w e r
around as much as possible to re­
m o to r to b lo w e r
create short c irc u it. W atch and listen
relay.
fo r arcing.
( L A M P DOES N O T L IG H T ]
Use 12 v o lt test lig h t a nd c h eck
w ire te rm in a ls a t re s is to r.
L A M P O FF
_ L
C heck F E E D w ire fro m
re sisto r to b lo w e r
speed s w itc h .
I L A M P O N | | l a m p o f f |
T
T
R eplace b lo w e r
R e pa ir o pen in w ire
speed s w itc h .
fro m b lo w e r speed sw itch .
E L E C T R I C A L S Y S T E M D I A G N O S T I C C H A R T
| f u s e o k !
T h e fo llo w in g tests sh o u ld be m ade
w it h th e ig n itio n s w itc h in ''R u n ''
p o s itio n , h ea ter o r A /C on and
b lo w e r s w itc h on h ig h .
C heck b lo w e r m o to r g ro u n d
T E S T L IG H T D O E S N O T
G R O U N D OK
L IG H T O N A L L T E R M IN A L S
C heck m o to r c o n n e c to r w ith
12 v o lt te st lig h t.
-L
L A M P D O E S N O T L IG H T
C heck w ire c o n n e c to r on
b lo w e r re la y w it h 12 v o lt te s t lig h t.
L A M P L IG H T S IN A L L
| L A M P D O E S N O T L IG H | C o n n e c t 12 v o lt te s t lig h t a t w ire
t
te rm in a l on b lo w e r re la y (w ire
fro m re sisto r to b lo w e r re la y ).
C heck w ire c o n n e c to r o n b lo w e r
re la y w it h 12 v o lt te s t lig h t.
|
l a m p u g h t s
I !
l a m p l i g h t s
Replace b lo w e r re la y.
Replace re la y
L A M P L IG H T S
R eplace re sis to r
Fig. 102-Electrical System Diagnosis Chart
BLOW ER M OTOR IN O P E R A T IV E
(C E R T A IN SPEEDS-EXCEPT HIGH
OIM C-K FO U R -S EAS O N )
Disconnect resistor connectors, connect one lead
of a self powered test lig h t to any one term inal
and use the other lead to probe each o f the
other term inals.
T E S T L IG H T L IG H T S ON
............. 1 ..................
R eplace re sisto r
W ith ig n itio n switch in " R u n " p osition and heater
or A /C on, use 12 v o lt test lamp to check fo r
voltage at resistor connector w ith b low er speed
switch in each position.
P O S IT IO N S
L A M P D O E S N O T L IG H T IN A L L P O S IT IO N S
Turn ig n itio n key o ff and p u t Heater or A /C
C ontrol in o ff position.
connector disconnected, connect a ju m pe r lead
fro m battery positive term inal to the w ire term in al
in connector.
voltage at w ire at blow er speed switch connector.
] [ L A M P D O E S N O T L IG H T !
Repeat same test on the other wires.
R e pa ir o pe n in w ire
fro m re sisto r to
b lo w e r re la y.
LA M P LIG H TS ON
A L L W IRES
Replace b lo w e r speed
s w itc h .
A L L T E R M IN A L S
I
T
1
W ith blow er resistor w ire
Use 12 v o lt test lig h t to check fo r
I
LA M P DOES N O T L IG H T
ON A L L W IRES
R e p a ir o p e n in
a ffe c te d w ire .