Chevrolet Light Duty Truck 1973, Service Manual

Page: 109 / 979

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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
B L O 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. sw itch in " R u n " position
and heater or A /C on, locate short in
one o f the fo llo w in g wires: (see note)
C-K Four-Season System
1. From fuse panel to master
switch on co n tro l.
2. From master switch to compressor
clu tch.
3. Master sw itch to blow er switch.
4. From blow er speed switch to
resistor.
5. From resistor to b low er m otor.
Except C-K Four-Season
1. From fuse panel to blow er switch.
2. From blow er switch to resistor.
3. From resistor to blo w e r m otor.
NO TE: S h o rt c irc u it may be in te r­
m itte n t.
If tester does not indicate
a short c irc u it, move heater harness
around as much as possible to re­
create short c irc u it. W atch and listen
fo r arcing.
L A M P O FF
_ L
|
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 e a te r o r A /C o n and
b lo w e r s w itc h on h ig h .
BLOW ER M OTO R IN O P E R A T IV E
(C E R T A IN SPEED S-EX CEP T HIG H
OIM C-K FO U R -S E A S O N )
Disconnect resistor connectors, conn ect one lead
o f 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.
C h eck b lo w e r m o to r g ro u n d
|P O O R OR NO G R 0 U N D |
I Repair g ro u n d |
G R O U N D OK
T E S T L IG H T D O E S N O T
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 ............. 1 ..................
12 v o lt te s t lig h t.
R eplace re sisto r
T E S T L IG H T L IG H T S ON
A L L T E R M IN A L S
| L A M P L IG H T S ]
-L
L A M P D O E S N O T L IG H T
I
W ith ig n itio n switch in " R u n " p o sitio n and heater
or A /C on, use 12 v o lt test lamp to check fo r
voltage at resistor conn ector w ith b lo w e r speed
switch in each position.
Replace m o to r
C heck w ir e 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.
T
|L A M P L IG H T S ! | L A M P D O E S N O T L IG H
t
|
L A M P L IG H T S IN A L L P O S IT IO N S
1
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
R epair o p e n in
w ire fr o m b lo w e r
m o to r to b lo w e r
relay.
C h eck w ir e 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.
C o n n e c t 12 v o lt te s t lig h t a t w ire
te r m in a l on b lo w e r re la y (w ire
fr o m re s is to r to b lo w e r re la y ).
( 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 e ck
w ir e te rm in a ls a t re s is to r.
I
l a m p l i g h t s
!
Re place re la y
|
l a m p u g h t s
] [ L A M P D O E S N O T L IG H T !
R e place b lo w e r re la y .
R e p a ir o p e n in w ir e
fr o m re s is to r to
b lo w e r re la y.
Turn ig n itio n key o ff and p u t Heater o r A /C
C o ntrol in o ff position. W ith blow er resistor w ire
conn ector disconnected, connect a ju m p e r lead
fro m b atte ry positive term inal to the w ire te rm in a l
in connector. Use 12 v o lt test lig h t to check fo r
voltage at w ire at blow er speed switch conn ector.
Repeat same test on the other wires.
I
L A M P L IG H T S
LA M P LIG H T S ON
A L L W IR ES
Re place b lo w e r speed
s w itc h .
LA M P DOES N O T L IG H T
ON A L L W IR ES
R e p a ir o p e n in
a ffe c te d w ire .
C heck F E E D w ir e fro m
re sisto r to b lo w e r
speed s w itc h .
R eplace re s is to r
I L A M P O N |
T
R e place b lo w e r
speed s w itc h .
|
l a m p o f f
|
T
R e p a ir o pe n in w ire
fr o m b lo w e r speed s w itc h .
Fig. 102-Electrical System Diagnosis Chart
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