Chevrolet 1980 Light Duty Truck Service Manual page 33

NO AIR FLOW
I
CHECK DEFROSTER OUTLETS FOR AIR FLOW
(If in d o u b t as to High or L o w air flo w
set selector on DEF w h ich is High and
compare. Reset selector on Heater)
I NO OR LOW AIR FLOW
J _ .........
CHECK HEATER OUTLET AIR FLOW
( If in d ou bt, sw itch fan
sw itch fro m Hi to Lo)
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CHANGE IN AIR FLOW
NORMAL AIR FLOW
Check heater o u tle t tem perature
w ith 220 F range the rm om ete r.
(a p pro xim ate o u tle t air tem peratures)
O utle t A ir 145
A m b ien t A ir 0
NORMAL TEMPERATURE
Remove all o b stru c tio n s under fro n t seat.
Car does n o t b u ild up heat - operate vent
co n tro ls and see th a t the air vent doors
close c o m p le te ly , if n ot, adjust.
LOW TEMPERATURE
(Check th e system tem pe ra ture a fte r re ­
pairing th e item checked to co m p lete th e
diagnosis.)
Check c o ola n t level; if lo w , f ill. L o o k fo r
or feel all ra d iato r and heater hoses and
conn ectio 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 required.
Check heater and ra d ia to r hoses fo r k in ks
straighten and replace as necessary.
Check tem pe ra ture d o o r fo r max heat po­
s itio n . A d ju st if necessary.
....... ....... I - ---------------
H E A T E R CORE
Feel tem peratures o f heater in le t and o u tle t hoses.
WARM INLET AND OUTLET HOSES
— r ...................
Check engine the rm osta t.
| HOT INLET AND WARM OUTLET HOSES
Check pulleys, b e lt ten sio n, etc., f o r p ro ­
per operation. Replace or service as neces­
sary.
Remove hoses fro m heater core. Reverse
flush w ith tap w ater. If plugged, repair or
replace.
INSUFFICIENT HEAT DIAGNOSIS
Position the co n tro ls so th a t the:
Tem perature lever is on fu ll heat.
Selector o r heater lever is on Heater.
Fan sw itch is on Hi.
•CHECK DUMP DOOR OUTLET FOR AIR FLOW
.
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 line
co nn ectio n w ith a vo ltm e te r.
UNDER 10 VOLTS
Check b a tte ry vo lts - u nd er 10 volts,
recharge the n recheck m o to r voltage.
Check w irin g and conn ectio n s for
under 10 v o lts fro m m o to r to fan
sw itch. Repair or replace last p o in t
o f under 10 v o lt reading.
A p p ly external ground, (jum p e r w ire) to
m o to r case. IN C R E A S E D A IR FLOW -
repair ground.
SAM E A l R FLO W - remove m o to r and
check fo r o b s tru c tio n in system o pe n ­
ing. I f none, R E PLACE M O TO R . If
o b s tru c tio n , remove m aterial and re­
install m o tor.
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A d ju st d u m p d oo r fo r no air flo w .
HIGH AIR FLOW
A djust defro ster d o o r fo r lo w air flo w .
LITTLE OR NO CHANGE IN AIR FLOW
[ OR NO AIR FLOW |
l o w
**C h e c k s h u to ff d oo r p o s itio n fo r fu ll
system air flo w . A d ju st if necessary.
LOW AIR FLOW
FUSE B LO W N - replace fuse.
A lR FLOW - system okay.
OVER 10 VOLTS
i :
FUSE R E M A IN S O K - remove m o to r
and check fo r o b s tru c tio n in system
opening, if none, R E PLACE M O TO R .
If o b s tru c tio n , remove m aterial and
re -in sta ll m o tor.
•C H E C K FOR C-K M O DELS
O N L Y
•C H E C K FOR G MO DELS
O N LY
HEATER 1A-5
NO AIR FLOW
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CHECK FUSE
BLOWS FUSE
Remove p ositive lead fro m m o to r and
replace fuse.
BLOWS FUSE - check fo r shorted
w ire in blow er electric c irc u it -
See Heater C ircu it Diagnostic Chart.
FUSE O K - See Heater C irc u it
D iagnostic C hart.
LIGHT T R U C K S E R V IC E MANUAL