GMC 4000 Series Service Manual page 100

EXPANSION VALVE REPLACEMENT
NOTE: When refrigeration system components
other than the com pressor are replaced, the com­
pressor must also be removed and oil drained
from the com pressor if oil was sprayed in copious
amounts due to leaks or collision damage to valve.
See "Checking Compressor Oil Level and Adding
Oil" explained previously.
1. Depressurize the system .
2. Drain the cooling system .
3. Remove the evaporator and heater core
unit from under dash as directed later under "Evap­
orator, Heater Core and Blower Replacement."
4. Remove the heater core from unit after re­
moving unit lower cover.
5. Disconnect expansion valve capillary tube
bulb at evaporator outlet pipe.
6. Disconnect expansion valve equalizer line
at suction throttling valve.
7. Disconnect thermostatic expansion valve
inlet and outlet connections carefully, as some
pressure may still exist, and plug openings.
8. Separate unit upper cover, then lift out the
coil assem bly. Remove expansion valve, noting
amount of oil that drains from fittings, and plug
openings.
9. Replace by reversing the previous pro­
cedure, using new rubber O-ring seals, well lub­
ricated with clean com pressor oil, at each fitting
connection.
10. Evacuate and charge system .
11. Make a performance test.
SUCTION THROTTLING VALVE
REPLACEMENT
NOTE: When refrigeration system components
other than the com pressor are replaced, the com­
pressor must also be removed and oil drained
from the com pressor if oil was sprayed in copious
amounts due to leaks or collision damage to core.
See "Checking Compressor Oil Level and Adding
Oil" explained previously.
1. Depressurize the refrigeration system .
2. Disconnect expansion valve equalizer line
at the suction throttling valve plug openings.
3. Disconnect suction valve to compressor
hose elbow.
4. Disconnect suction valve from evaporator
outlet. Remove two bracket attaching cap screws,
then remove valve.
5. Replace the suction throttling valve by re­
versing the above procedures, using new rubber
O-ring seals, well lubricated with com pressor oil,
at each connection.
6. Evacuate complete system .
7. Charge complete system .
8. Make a performance test.
G M C S E R V I C E M A N U A L
other than the com pressor are replaced, the com ­
pressor must also be removed and oil drained
from the com pressor if oil was sprayed in copious
amounts due to leaks or collision damage to valve.
See "Checking Compressor Oil Level and Adding
Oil" explained previously.
cables. Also, disconnect blower motor ground wire
at dash.
floor opening.
right side cowl. There are two at the top and bot­
tom of unit.
bolt. Carefully remove unit from cab.
duct assembly by reversing previous procedures.
will determine the extent of repair required. Good
judgment must be used in deciding what steps are
necessary to put the system back into operation.
spected. No attempt should be made to straighten
kinked tubes or repair any bent or broken units.
Check especially for cracks at soldered connections.
REFRIGERATION SYSTEM
OPEN TO ATMOSPHERE
and dirt to enter. These parts should be sealed as
soon as possible until such time as they are re­
placed.
minutes (depending on humidity), the receiver-
dehydrator assembly will absorb an excessive
amount of moisture and should be replaced, and
each component of the system should be cleaned
with dry nitrogen and flushed with liquid refriger­
ant to remove dirt and moisture.
FLUSHING SYSTEM
refrigerant drum to the unit to be flushed and then
turning the drum upside down and opening the drum
AIR CONDITIONING
EVAPORATOR HEATER CORE
ASSEMBLY REPLACEMENT
NOTE: When refrigeration system components
1. Depressurize the system.
2. Drain coolant.
3. Disconnect heater hoses at cowl.
4. Disconnect air distributor tube from blower.
5. Disconnect all heating and cooling control
6. Disconnect refrigerant hoses from unit.
7. At base of unit, pull the drain tube from
8. Remove four screw s which attach unit to
9. At front of cowl remove single attaching
10. Replace evaporator unit and blower motor
11. Evacuate and charge system .
12. Make a performance test.
COLLISION SERVICE
The severity and circum stances of the collision
Each part of the system must be carefully in­
Broken tubes or units will allow air, moisture
If the system is open for more than 15 or 20
Flushing can be accomplished by connecting a
Sec. 1
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