Insufficient Cooling - Chevrolet LIGHT DUTY TRUCK (SERIES 10-35) Service Manual

CONDITION AND CAUSE
Heater outlet Temperature too low.
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EVAPORATOR
When the evaporator is defective, the trouble will show
up as an inadequate supply of cool air. A partially plugged
core due to dirt, a cracked case, or a leaking seal will
generally be the cause.
REFRIGERANT LINE RESTRICTIONS
Restrictions in the refrigerant lines will be indicated as
follows:
1. Suction Line - A restricted suction line will cause
low suction pressure at the compressor, low discharge
pressure and little or no cooling.
2. Discharge Line - A restriction in the discharge line
generally will cause the pressure relief valve to open.
3. Liquid Line - A liquid line restriction will be
evidenced by low discharge and suction pressure, and

insufficient cooling.

S ig ht Glass Diagnosis (M o to r Hom e Chassis
Units)
At temperatures higher than 70°F (21°C), the sight
glass may indicate wheter the refrigerant charge is
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CORRECTION
Check duct work for proper installation.
Check blower operation.
Inspect TEMP lever and cable for proper
operation.
Check heater hoses for function.
On A, B and G Series check water
control valve as follows:
1. Start engine and allow to warm up.
2. Set control panel for M A X mode.
3. Feel hose from water valve to
heater core.
Hose should not be hot. This indicates
that vacuum is applied to the water
control valve and that the water supply
to the heater core is shut off. In any
other position of the control panel selector
(mode) lever, water should flow to the
heater core. If not, check water control
valve and vacuum supply hose.
4. On B Series, C60 Custom A/C, vacuum
should be applied and water flow should
stop as temperature lever is moved to
maximum COLD position in any A /C mode
position.
sufficient. A shortage of liquid refrigerant is indicated after
above five minutes of compressor operation by the
appearance of slow-moving bubbles (vapor) or a broken
column of refrigerant under the glass. Continuous bubbles
may appear in a properly charged system on a cool day. This
is a normal situation. If the sight glass is generally clear and
performance is satisfactory, occasional bubbles do not
indicate refrigerant shortage.
If the sight glass consistently shows foaming or a
broken liquid column, it should be observed after partially
blocking the air to the condenser. If under this condition
the sight glass clears and the performance is otherwise
satisfactory, the charge shall be considered adequate.
In all instances where the indications of refrigerant
shortage continues, additional refrigerant should be added
in 1/4 lb. increments until the sight glass is clear. An
additional charge of 1/2 lb. should be added as a reserve
after the glass clears. In no case should the system be
overcharged.
AIR CONDITIONING
LIGHT T R U CK S ER V IC E M ANUAL
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