Chevrolet Light Duty Truck 1973, Service Manual

Page: 37 / 979

HEATER A N D AIR C O N D IT I O N IN G 1A-11
INSUFFICIENT HEAT DIAGNOSIS
P o s itio n th e c o n tro ls so th a t the :
T e m p e ra tu re lever is o n fu ll heat.
S elector o r heater lever is o n Heater.
Fan sw itch is o n Hi.
•CHECK DUMP DOOR O UTLET FOR A IR FLOW
NO AIR FLOW
CHECK DEFROSTER OUTLETS FOR AIR FLOW
( I f in d o u b t as to High o r L o w a ir flo w
set selector o n DE F w h ic h is High and
co m pare. Reset selector on Heater)
A d ju s t d u m p d o o r fo r no a ir flo w .
| NO OR LOW AIR FLOW |
CHECK HEATER O UTLE T A IR FLOW
( If in d o u b t, sw itch fan
sw itch fro m Hi to L o)
| HIGH AIR FLOW |
A d ju s t d e fro s te r d o o r fo r lo w a ir flo w .
CHANGE IN AIR FLOW
Z . I ...—
NORM AL AIR FLOW
Check heater o u tle t te m p e ra tu re
w ith 2 20
F range th e rm o m e te r.
(a p p ro x im a te o u tle t a ir tem pe ra tures)
O u tle t A ir 145 150 155 165
A m b ie n t A ir 0 2 5 40 75
NORM AL TEMPERATURE
Rem ove a ll o b s tru c tio n s u nd er fr o n t seat.
Car does n o t b u ild up heat - o pe ra te ve n t
c o n tro ls and see th a t th e a ir ve n t d oo rs
close c o m p le te ly , if n o t, a dju st.
LOW TEMPERATURE
I E
(C heck th e system te m p e ra tu re a fte r re ­
p a irin g th e ite m ch ecked to c o m p le te th e
diagnosis.)
Check c o o la n t level; if lo w , f ill. L o o k fo r
o r feel all ra d ia to r and heater hoses and
co n n e c tio n s fo r leaks. Repair o r replace.
Check th e ra d ia to r cap fo r damage and re­
place if re q u ire d .
Check heater a nd ra d ia to r hoses fo r k in k s
stra ig hte n and replace as necessary.
Check te m p e ra tu re d o o r fo r m ax heat p o ­
s itio n . A d ju s t if necessary.
| HEATER CORE |
| Feel tem pe ra tures o f heater in le t and o u tle t hoses. [
WARM IN LE T AND O UTLET HOSES
Check engine th e rm o s ta t.
LITTLE OR NO CHANGE IN A IR FLOW |
LOW OR NO A IR FLOW
LOW A IR FLOW
Check heater o u tle t fo r o b s tru c tio n - re ­
move.
Check m o to r vo ltag e a t closest m o to r lin e
c o n n e c tio n w ith a v o ltm e te r.
UNDER 10 VOLTS OVER 10 VO LTS
C heck b a tte ry v o lts - u nd er 10 v o lts,
recharge th e n recheck m o to r vo ltage.
C heck w irin g and c o n n e c tio n s fo r
u nd er 10 v o lts fro m m o to r to fan
s w itch . Repair o r replace last p o in t
o f u nd er 10 v o lt reading.
A p p ly e xte rn a l g ro u n d , (ju m p e r w ire) to
m o to r case. IN C R E A S E D A l R F L O W -
re p air g ro un d.
S A M E A l R F L O W - rem ove m o to r and
check f o r o b s tru c tio n in system o p e n ­
ing. I f none, R E P LA C E M O T O R . If
o b s tru c tio n , rem ove m a terial and re ­
in stall m o to r.
* *C h e c k s h u to ff d o o r p o s itio n fo r fu ll
system a ir flo w . A d ju s t if necessary.
NO A IR FLOW
CHECK FUSE
FUSE B LO W N - replace fuse. I
A IR F L O W - s y s te m o ka y.
BLOWS FUSE
Remove p o s itiv e lead fro m m o to r and
replace fuse.
FUSE R E M A IN S O K - rem ove m o to r
and check fo r o b s tru c tio n in system
ope ning , if none, R E P LA C E M O T O R .
If o b s tru c tio n , rem ove m a terial and
re -in s ta ll m o to r.
BLO W S FUSE - check fo r sh orte d
w ire in b lo w e r e le ctric c ir c u it -
See Heater C irc u it D ia g no stic C h art.
FUSE OK |
FUSE O K - See Heater C irc u it
D iagnostic C h a rt.
| HOT IN LE T AND WARM O U TLE T HOSES |
Check p u lle ys, b e lt te n s io n , e tc., f o r p ro ­
per o p e ra tio n . Replace o r service as neces­
sary.
I ............
Rem ove hoses fro m heater core. Reverse
flu s h w ith ta p w a te r. I f plugged, re p air o r
replace.
'CH ECK FOR C-K MODELS
ONLY
■CHECK FOR G MODELS
ONLY
LIGHT DUTY TRUCK SERVICE MANUAL