Chevrolet Light Duty Truck 1973 Service Manual page 110

BLOW ER M O TO R IN O P E R A T IV E
A T H IG H SPEED O N LY
(C-K FO U R -SEASO N SYSTEM )
Check
in-line fuse
FUSE BLO W N
C onnect Tester. Use to check
w ire fro m ju n c tio n to b lo w e r
relay to locate sh o rt. Repair
sh o rt c irc u it as .re q u ire d .*
CL ICK H E A R D
I 1
Check w ire te rm in a l on relay
th a t goes to ju n c tio n blo ck
w ith 12 v o lt test lam p.
X
j
LA M P L IG H T S
|L A M P DOES N O T L IG H T | LA M P LIG H T S |
___ _ 1
1
1
Repair open in w ire
Replace b lo w e r fro m ju n c tio n b lo ck Check ground
relay. on relay
to relay.
|G R O U N D O K | | b a d g r o u n d
Replace relay R epair ground
* S h o rt c irc u it m ay be in te rm itte n t.
If tester does n o t indicate a s h o rt c irc u it,
m ove harness arou nd as m uch as possible
to re-create sh o rt c irc u it. W atch and
listen fo r arcing.
**R e fe r to W iring Diagrams w hile performing
the follow ing checks.
ELECTRICAL SYSTEM D IA G N O S T IC CHART
W ith ig n itio n sw itch in " R u n " p o s itio n , and
| F U S E O K |
tester and locate s h o rt in one o f the fo llo w in g w ires or co m p o ­
nents. Replace a shorted w ire o r defe ctive sw itch .
W ith ig n itio n sw itch in the
C-K M O D E L S YSTEM S
" R u n " p o sitio n and the
1. W ire fro m fuse panel to m aster sw itch (on c o n tro l).
heater o r A /C on, m ove the
Master sw itch .
2.
blow e r speed sw itch to H i.
3. W ire fro m m aster sw itch to th e rm o sta tic sw itch .
Relay " c lic k " should be
4. T h e rm o sta tic sw itch .
heard when sw itch is m oved.
5. W ire fro m th e rm o s ta tic sw itch to discharge pressure sw itch .
6. Discharge pressure sw itch .
I '
I NO C LIC K H E A R D !
7. W ire fro m discharge pressure sw itch to com pressor clu tc h
_
solenoid.
G M O D E L SYSTEM S
Check relay c o il c o n n e cto r
1. W ire fro m fuse panel to blow e r sw itch .
w ith 12 v o lt te st lig h t.
B low er sw itch .
2.
3. W ire fro m b lo w e r sw itch to th e rm o s ta tic sw itch .
T h e rm o sta tic sw itc h .
4.
5. W ire fro m th e rm o sta tic sw itch to the rm a l fuse.
| lA M P DOES N O T L IG H T |
6. Therm al fuse.
f—*
7. W ire fro m the rm a l fuse to com pressor c lu tc h solen oid.
Check w ire term in a l on b lo w e r
M O TO R H O M E U N IT
speed sw itch c o n n e cto r w ith
1. W ire fro m fuse panel to blow e r sw itch .
12 v o lt test lig h t.
2. B low e r sw itch .
3. W ire fro m b lo w e r sw itch to th e rm o s ta tic sw itch .
4. T h e rm o sta tic sw itch .
r i
5. W ire fro m th e rm o s ta tic sw itch to com pressor clu tc h
solenoid.
| |L A M P L IG H T S | L A M P DOES
N O T L IG H T 1
1
Repair open Replace
in w ire fro m
B lo w e r speed
blow e r speed sw itch .
sw itch to relay.
Fig. 103-Electrical System Diagnosis Chart
COM PRESSOR C LU TC H IN O P E R A T IV E 1
... 1
Check fuse
X
FUSE B LO W N
Check C om pressor S ole noid G round
" O n " , connect
A /C
|P O O R OR NO G R O U N D l
Repair ground
X
NO C L IC K H E A R D
Replace solenoid
W ith ig n itio n sw itch in " R u n " p o s itio n and A /C " O n " , check
fo r defective sw itch at the fo llo w in g locations. Using an exte rnal
ju m p e r w ire , d isco nnect the electrical lead at the sw itch and
ju m p the sw itch te rm in a ls (see "W irin g D iagra m s").
C-K M O D E L SYS T E M
1. Master S w itch .
2. T h e rm o sta tic S w itch .
3. Discharge Pressure S w itch .
G M O D E L SYS T E M
1. B low e r sw itch .
2. T h e rm o sta tic S w itch .
3. T herm al fuse (See " L o w R e frig e ra n t Charge P ro te ctio n System
D iagn osis").
M O T O R H O M E U N IT
1. B low e r sw itch .
2. T h e rm o sta tic sw itch .
N O T E : If th e com pressor is still in o p e ra tive a fte r the above
checks, check fo r pow er feed at each co m p o n e n t since
tw o or m ore co m p o n e n ts are defe ctive or there is an
open in the w ires co nn ecting the com p onents.
[ FUSE O K |
( G R O U N D 0~iT|
Disconnect conn ector on
com pressor clu tc h solenoid
and a p p ly 12 vo lts to solenoid.
C LIC K H E A R D