Chevrolet Light Duty Truck 1973 Service Manual page 75

CHECKING OIL
In the six cylinder compressor it is not recommended
that the oil be checked as a matter of course. Generally,
compressor oil level should be checked only where there
is evidence of a major loss of system oil such as might be
caused by:
• A broken refrigerant hose
• A severe hose fitting leak
• A very badly leaking compressor seal
• Collision damage to the system components
As a quick check on compressor oil charge, operate the
engine at on maximum cold for approximately 10
idle
minutes, turn off the engine and momentarily crack open
the oil drain plug on bottom of the compressor letting a
slight amount of oil drain out. Retighten plug. Again
slightly crack open the plug. If oil comes out, the
compressor has the required amount of oil.
NOTE: The oil may appear foamy. This is
considered normal.
To further check the compressor oil charge, should the
above test show insufficient oil, it is necessary to remove
the compressor from the vehicle, drain and measure the
oil as outlined under "Checking Compressor Oil
Charge."
Checking Compressor Oil Charge
1. Run the system for 10 minutes at 500-600 engine
rpm with controls set for maximum cooling and
high blower speed.
2. Turn off engine, discharge the system, remove
compressor from vehicle, place it in a horizontal
position with the drain plug downward. Remove the
drain plug and, tipping the compressor back and
forth and rotating the compressor shaft, drain the
oil into a clean container, measure and discard the
oil.
3. Add new refrigeration oil to the compressor as
follows.
a. If the quantity drained was 4 fluid oz. or more,
add the same amount of new refrigeration oil to
the replacement compressor.
HEATER A N D AIR C O N D IT IO N IN G
b. If the quantity drained was less than 4 fluid oz.,
add 6 fluid oz. of new refrigeration oil to the
replacement compressor.
c. If a new service compressor is being installed,
drain all oil from it and replace only the amount
specified in Steps 3a and 3b above.
d. If a field repaired compressor is being installed,
add an additional 1 fluid oz. to the compressor.
4. In the event that it is not possible to idle the
compressor as outlined in Step 1 to effect oil return
to it, proceed as follows:
a. Remove the compressor, drain, measure and
discard the oil.
b. If the amount drained is more than 1-1/2 fluid
oz. and the system shows no signs of a major
leak, add the same amount to the replacement
compressor.
c. If the amount drained is less than 1-1/2 fluid oz.
and the system appears to have lost an excessive
amount of oil, add 6 fluid oz. of clean
refrigeration oil to replacement compressor, 7
fluid oz. to a repaired compressor.
If the oil contains chips or other foreign
material, replace the receiver-dehydrator (expan­
sion tube on C-K models) and flush or replace all
component parts as necessary. Add the full 11
fluid oz. of new refrigeration oil to the
replacement compressor.
5. Add additional oil in the following amounts for any
system components being replaced.
Evaporator C ore....................................... 3 fluid oz.
Condenser................................................... 1 fluid oz.
Receiver-Dehydrator............................... 1 fluid oz.
Accum ulator............................................... 1 fluid oz.
When adding oil to the compressor,
CAUTIO N:
it will be necessary to tilt the rear end of the
compressor up so that the oil will not run out of
the suction and discharge ports. Do not set the
compressor on the shaft end.
1A-49
LIGHT DUTY TRUCK SERVICE MANUAL