GMC 1982 Light Duty Truck Service Manual page 30

N O A IR F L O W
C H E C K D E F R O S T E R O U T L E T S F O R A IR F L O W
(If in d o ubt as to H igh or L o w air flo w
set selector on D E F w hich is High and
com pare. Reset selector on Heater)
I N O O R L O W A IR F L O W I
I
C H E C K H E A T E R O U T L E T A IR F L O W
(If in d o u b t , sw it c h fa n
sw itc h f r o m H i t o L o )
C H A N G E IN A IR F L O W
..............1
N O R M A L A IR F L O W
Check heater o u tle t tem p e ratu re
w ith 220° F range th erm o m eter.
(ap p ro xim ate o u tle t air tem peratures)
O u tle t A ir 145
A m b ie n t A ir 0
| N O R M A L T E M P E R A T U R E
Rem ove all obstructions under fro n t seat.
Car does not b uild up heat - operate vent
controls and see th a t the air vent doors
close co m p letely, if not, adjust.
LO W T E M P E R A T U R E
(Check th e system tem p e ratu re a fte r re ­
pairing th e item checked to co m p lete th e
diagnosis.)
Check co ola nt level; if lo w , fill. L o o k for
or feel all rad ia to r and heater hoses and
connections for leaks. Repair or replace.
Check th e rad ia to r cap for dam age and re­
place if required.
Check heater and radiator hoses fo r kinks
straighten and replace as necessary.
---------------
Check tem p e ratu re d oor fo r m ax heat po­
sition. A djust if necessary.
........ ................j-------------
H E A T E R C O R E
[ Feel tem peratures o f heater inlet and o u tle t hoses. |
W A R M IN L E T A N D O U T L E T H O S E S I
~ 'I " ---------- '
Check engine therm ostat. I
H O T IN L E T A N D W A R M O U T L E T H O S E S
Check pulleys, belt tension, etc., fo r p ro ­
per o p era tio n . Replace or service as neces­
sary.
Rem ove hoses fro m heater core. Reverse
flush w ith tap w ate r. If plugged, repair or
replace.
I N S U F F I C I E N T H E A T D I A G N O S I S
Position th e contro ls so th a t the:
Tem p erature lever is on fu ll heat.
Selector or heater lever is on Heater.
Fan switch is on H i.
•C H E C K D U M P D O O R O U T L E T F O R A IR F L O W
•*
I
1 .........................
150 155 165
40 75
2 5
Check heater o u tle t for obstru ction - re ­
move.
Check m o to r voltage at closest m o to r line
connection w ith a vo ltm eter.
U N D E R 10 V O L T S | [ O V E R 10 V O L T S |
X
Check b a tte ry volts - under 10 volts,
recharge th en recheck m o to r voltage.
Check w irin g and connections for
under 10 volts fro m m o to r to fan
sw itch. Repair or replace last point
o f under 10 vo lt reading.
E
I —
A pply external ground, (jum p er w ire) to
m o to r case. IN C R E A S E D A IR F L O W -
repair ground.
S A M E A IR F L O W - rem ove m o to r and
check fo r o b stru ction in system o p en ­
ing. If none, R E P L A C E M O T O R . If
o bstru ction, rem ove m aterial and re­
install m otor.
" I -------
A IR F L O W
I
Adjust d um p door for no air flo w .
I H IG H A IR F L O W
I
[ Adjust defroster d oor for low air flo w . |
L IT T L E O R N O C H A N G E IN A IR FL O W
L O W O R N O A IR F L O W
" C h e c k sh u to ff door position fo r full
system air flo w . A djust if necessary.
| LO W A IR F L O W [
'CHECK FOR C K M O D ELS
ONLY
' CHECK FOR G M ODELS
O NLY
HEATER
I
| N O A IR F L O W
C H E C K FU S E
FU S E B L O W N - replace fuse.
1 ...... ......
A IR F L O W - system okay.
B LO W S FUSE
Remove positive lead fro m m o to r and
replace fuse.
FU S E R E M A IN S O K - remove m otor
and check for obstru ction in system
opening, if none, R E P L A C E M O T O R .
If ob stru ctio n , remove m aterial and
re-install m o to r.
BLO W S FU S E - check for shorted
w ire in blow er electric circu it -
See H eater C ircu it Diagnostic C hart.
| FUSE O K
FUSE O K - See H eater C ircu it
Diagnostic C hart.
1A-5
|