Collision Service - Chevrolet 70 Series 1970 Service Manual

If a ir distributor is rem oved from main heater
housing, during a ssem b ly u se a se a le r at the m at­
ing su rfa ces between the two components to p re ­
vent a ir lea k s.
INSTALLATION
1. With the aid of an a ssista n t, carefu lly p o si­
tion main heater housing and air distributor a s ­
sem bly in the cab on the engine tunnel.
2. Install bolts that retain main heater housing
and sle e p e r heater (when used) to engine cover.
3. Attach heater and d efroster h o ses to a ir
distributor. Retain h o ses in position with p la stic
clam p s.
4. On m odels equipped with sleep er com part­
ment heater, lift up m a ttress and plywood support,
then se c u r e sle e p e r ducts to sle e p e r heater outlets
with p la stic clam ps.
5. Connect a ll heating and cooling control
cab les (refer to fig s . 4 and
NOTE: Each control cable is equipped with a
threaded sle e v e which can be adjusted to a ssu re
proper cable operation.
. Connect e le c tr ic a l lea d s to a ir conditioning
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sw itch mounted on a ir distributor and blow er m otors
7. Attach coolant lin e s to main heater core
and sle e p e r heater co re (when u sed ).
. Connect the refrigeran t lin e s to expansion
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valve and P.O .A . valve.
NOTE: B e su r e to u se new O -ring s e a ls which
a re w ell lubricated with clean co m p ressor oil at
refrigeran t lin e connections.
9. Connect battery ground cable.
10. Evacuate and charge the sy ste m . R efill
cooling sy ste m , Check perform ance of A /C and
heating s y ste m s.
11. Install a c c e s s panel and heater cover a s
d escrib ed p reviou sly in this section .
EVAPORATOR HEATER CORE
ASSEMBLY REPLACEMENT
(CONVENTIONAL CAB)
(Refer to Figure 11)
NOTE: When refrigeration sy ste m components
other than the c o m p resso r a r e replaced, the com ­
p r e s so r m ust a lso be rem oved and oil drained
from the com p ressor, if o il w as sprayed in copious
amounts due to leak s or c o llisio n damage to valve.
See "Checking C om pressor O il L evel and Adding
Oil" explained p reviou sly.
1. D ep ressu rize the sy ste m .
2. D rain coolant.
3. D isconnect heater h o ses at cowl.
4. D isconnect air distributor tube from blow er.
5. D isconnect a ll heating and cooling control
ca b le s. A lso , disconnect blow er motor ground w ire
at dash.
).
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CAB AND BODY MOUNTINGS 1-137
. D isconnect refrigeran t h o ses from unit.
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7. At b a se of unit, pull the drain tube from
flo or opening.
. R em ove four sc r e w s which attach unit to
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right sid e cow l. There are two at the top and bot­
tom of unit.
9. At front of cowl rem ove sin g le attaching
bolt. C arefully rem ove unit from cab.
10. R eplace evaporator unit and blow er motor
duct a ssem b ly by r ev ersin g previous p ro ced u res.
11. Evacuate and charge sy ste m .
12. Make a perform ance te st.

COLLISION SERVICE

The se v er ity and circu m stan ces of the c o l­
lisio n w ill determ ine the extent of repair required.
Good judgment m ust be u sed in deciding what step s
a r e n e c e ssa r y to put the sy ste m back into operation.
Each part of the sy ste m m ust be carefully in ­
spected. No attem pt should be made to straighten
kinked tubes or rep air any bent or broken units.
Check esp ecia lly for crack s at soldered connections.
REFRIGERATION SYSTEM
OPEN TO ATMOSPHERE
Broken tubes or units w ill allow a ir , m oisture
and dirt to enter. T hese p arts should be se a led as
soon a s p o ssib le until such tim e a s they a re r e ­
p laced.
If the sy ste m is open for m ore than 15 or 20
m inutes (depending on humidity), the r e c e iv e r -
dehydrator assem b ly w ill absorb an ex c e ssiv e
amount of m oistu re and should be replaced, and
each component of the sy ste m should be cleaned
with dry nitrogen and flushed with liquid r e fr ig e r ­
ant to rem ove dirt and m oisture.
FLUSHING SYSTEM
Flushing can be accom plished by connecting a
refrigeran t drum to the unit to be flushed and then
turning the drum upside down and opening the drum
shut-off valve to fo rc e refrigeran t through the unit.
The unit should be supported so that the r e fr ig e r ­
ant p a ssin g through it w ill be directed into an area
w here -2 1 .7 ° F ., w ill do no damage.
CAUTION: Remember that when liquid
refrigerant is released from the drum
into an area where atmospheric pressure
exists, its temperature will immediately
drop to -21.7°F.
In order to keep the expansion valve open when
flushing the evaporator, the expansion valve bulb
m ust be detached from the evaporator outlet tube.
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL