Chevrolet Light Duty Truck 1973 Service Manual page 37

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 on DEF w h ic h is High and
com pare. Reset selector on Heater)
| NO OR LOW AIR FLOW |
CHECK HEATER OUTLET A IR FLOW
( If in d o u b t, sw itch fan
sw itch fro m Hi to Lo)
CHANGE IN AIR FLOW
Z .
NORMAL AIR FLOW
Check heater o u tle t te m pe ra ture
w ith 2 20 F range the rm o m e te r.
(a p p ro x im a te o u tle t a ir tem peratures)
O u tle t A ir
145
A m b ie n t A ir 0
NORMAL TEMPERATURE
Remove 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 perate ve nt
c o n tro ls and see th a t th e a ir ve nt d oors
close c o m p le te ly , if n o t, a djust.
LOW TEMPERATURE
(Check th e system te m p e ra tu re a fte r re ­
p airin g th e item checked 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
or 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 uired .
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 po­
s itio n . A d ju s t if necessary.
| HEATER CORE |
| Feel tem peratures o f heater in le t and o u tle t hoses. [
WARM INLE T AND OUTLET HOSES
Check engine th e rm o s ta t.
| HOT IN LET AND WARM O UTLET HOSES |
Check p u lleys, b e lt te n sio n , etc., f o r p ro ­
per o p e ra tio n . Replace o r service as neces­
sary.
Remove hoses fro m heater core. Reverse
flu s h w ith tap w a ter. I f plugged, re p air or
replace.
INSUFFICIENT HEAT DIAGNOSIS
P o sitio n th e c o n tro ls so th a t the:
T e m p eratu re lever is o n fu ll heat.
S elector o r heater lever is on Heater.
Fan sw itch is o n Hi.
•CHECK DUMP DOOR OUTLET FOR A IR FLOW
I ...—
150
155 165
25 40 75
Check heater o u tle t fo r o b s tru c tio n - re ­
move.
Check m o to r voltage at closest m o to r lin e
co n n e c tio n w ith a v o ltm e te r.
UNDER 10 VOLTS
I E
Check b a tte ry v o lts - u nd er 10 v o lts,
recharge th e n recheck m o to r voltage.
Check 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 exte rn a l g ro un 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 FLO W -
re p air g round.
S AM E A l R FLO 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 aterial and re ­
install m o to r.
I ............
HEATER A N D AIR C O N D IT IO N IN G
A d ju s t d u m p d o o r fo r no air flo w .
| 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 .
LITTLE OR NO CHANGE IN A IR FLOW
LOW OR NO A IR FLOW
* *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.
LOW A IR FLOW
FUSE B LO W N - replace fuse.
OVER 10 VOLTS
and check fo r o b s tru c tio n in system
opening, if none, R E P LA C E M O T O R .
If o b s tru c tio n , rem ove m aterial and
re -in s ta ll m o to r.
'CH ECK FOR C-K MODELS
ONLY
■CHECK FOR G MODELS
ONLY
1A-11
|
|
NO A IR FLOW
CHECK FUSE
I
A IR F L O W -s y s te m okay.
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
BLO W S FUSE - check fo r shorted
w ire in b lo w e r e lectric 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 art.
LIGHT DUTY TRUCK SERVICE MANUAL