Chevrolet 1977 light duty truck, Service Manual

Page: 38 / 861

N O T E : Be sure core to case and case to dash pane!
sealer is intact before assem bling unit.
G M odels
Replacem ent (Fig. 1A-9)
1. Disconnect the battery g round cable.
2. Place a clean p a n und er the vehicle and then
disconnect the heater core inlet and outlet hoses at the
core connections (see " H e a te r H oses-R eplacem ent" later
in this section). Quickly plug the heater hoses and
support them in a raised position. Allow the coolant in
the heater core to d ra in into the p a n on the floor.
3. Disconnect the right h a n d air distributor hose
fro m the heater case and rotate it up out o f the way.
4. Pry off the te m p e ra tu re door cable eyelet clip
an d then remove the bowden cable attaching screw.
5. Remove the distributor duct to heater case
screws an d pull the duct r e a rw a rd out o f the heater case
retainer.
6. Remove the four heater case to d ash screws and
th en remove the heater case an d core as an assembly.
Tilt the case assembly rearw ard at the top while lifting
up until the core tubes clear the dash openings.
7. Remove the core re ta in in g strap screws and
rem ove the core.
8. To install a new core, reverse Steps 1-7 above.
N O T E : Be sure core to case and case to dash panel
sealer is intact before assembling unit.
H EA TER HOSES
H eater hoses are routed from the tnerm ostat
housing or inlet m an ifo ld and w ater p u m p (radiator on
some autom atic transm ission vehicles) to the core inlet
and outlet pipes as shown in Figure 1 A - 10. Hoses are
attached at each end with screw type clamps.
R eplacem ent
T he heater core can be easily d a m a g e d in the area
o f the core tube attach m en t seams whenever undue force
is exerted on them. W hen ev er the heater core hoses do
not readily come off the tubes, the hoses should be cut
ju st forw ard o f the core tubes. The portion o f the hose
rem a in in g on the core tube should then be split
longitudinally. Once the hoses have been split, they can
be removed from the tubes without d am ag e to the core.
C EN TER D IS T R IB U T O R D U C T - G M odels
Replacem ent (Fig. 1A -11)
1. Disconnect the battery g round cable.
2. U n sn ap the engine cover front latches. Remove
the two cover to floorpan screws and remove the cover.
3. Remove the heater core case and core as an
a ssem bly (see " H e a t e r D is tr ib u to r an d Core-
Replacem ent").
4. Disconnect the right h a n d heater outlet hose
and the two defroster hoses from the distributor duct.
5. Disconnect the air and defroster door cables by
prying off the eyelet clips and removing the cable
attaching screws.
6. Pull the center distributor duct to the right and
remove it from the vehicle.
7. To install, reverse Steps 1-6 above.
N OTE: Check cable and door opeation; cables
should be free from kinks or binding and doors
should close properly. If cable adjustm ent is
necessary, see "Bowden Cable-A djustm ent."
LEFT D IS T R IB U T O R D U C T - G M odels
Replacem ent (Fig. 1A -11)
1. Disconnct the battery ground cable.
2. U n sn a p the engine cover front latches. Remove
the two cover to floorpan screws and remove the cover.
3. Remove the duct bracket screw and remove the
duct.
4. To install, reverse Steps 1-3.
N O TE: All three bowden cables are routed under
the duct. It m a y be necessary to hold the cables
down as the duct is being installed. Be sure the left
duct is fully installed over the center duct.
DEFROSTER DU C T
The defroster hose and outlet assemblies are
illustrated in Figure 1 A - 12.
C O N TR O L ASSEMBLY
C-K M odels
Replacem ent (Fig. 1A -13)
1. Disconnect the battery g ro u n d cable.
2. Remove the instrum ent p an el bezel.
3. Disconnect the bowden cables and the blower
switch wiring harness.