4-13
62--611XX--20 (03/04)
3. Check the level of the oil in the front sight glass with
the compressor operating. The correct level should
be between bottom and 1/4 of the sight glass. If the
level is above 1/4, oil must be removed from the
compressor. To remove oil from the compressor,
follow step d. If the level is below sight glass, add oil
to the compressor following step b.
b. Adding oil with compressor in system
Two methods for adding oil are the oil pump method
and closed system method.
1. Oil Pump Method
This oil pump adapts to a one U.S. gallon (3.785
liters) metal refrigeration oil container and pumps 2-1/2
ounces (0.0725 liters) per stroke when connected to the
suction service valve port. Also there is no need to
remove pump from can after each use.
When the compressor is in operation, the pump
check valve prevents the loss of refrigerant, while
allowing servicemen to develop sufficient pressure to
overcome the operating suction pressure to add oil as
necessary.
Backseat suction service valve and connect oil
charging hose to port. Crack the service valve andpurge
the oil hose at oil pump. Add oil as necessary.
2. Closed System Method
In an emergency where an oil pump is not available,
oil may be drawn into the compressor through the
suction service valve.
CAUTION
Extreme care must be taken to ensure
the manifold common connection
remains immersed in oil at all times.
Otherwise air and moisture will be
drawn into the compressor.
Connect the suction connection of the gauge
manifold to the compressor suction service valve port,
and immerse the common connection of the gauge
manifold in an open container of refrigeration oil. Crack
the suction service valve and gauge valve to vent a
small amount of refrigerant through the common
connection and the oil to purge the lines of air. Close the
gauge manifold valve.
With the unit running, frontseat the suction service
valve and pull a vacuum in the compressor crankcase.
SLOWLY crack the suction gauge manifold valve andoil
will flow through the suction service valve into the
compressor. Add oil as necessary.
c. Adding oil to service replacement compressor
Service replacement compressors may or may not
be shipped with oil.
If compressor is without oil :
Add correct oil charge (Refer to section 2.3) by
removing the oil fill plug (See Figure 4-8)
d. To remove oil from the compressor
1. Close suction service valve (frontseat) and pump
unit down to 0.1 to 0.3 kg/cm
@
(2 to 4 psig). Frontseat
discharge service valve and slowly bleed remaining
refrigerant.
2. Removethe oildrain plug fromcompressor anddrain
the proper amount of oil from the compressor.
Replace the plug securely back into the compressor.
3. Open service valves and run unit to check oil level,
repeat as required to ensure proper oil level.
4.11 COMPRESSOR UNLOADER VALVE -- FOR
SUPRA 850MT & 950MT ONLY
The compressor unloader (located on the
compressor cylinder head) is controlled by relay UFR
and the temperature controller.
a. Checkout procedure
1. Connect manifold gauges to the compressor suction
and discharge service valvesand start unit in cooling
with the setpoint temperature at least 5
_
F (2.8
_
C)
above set point and the compressor will be fully
loaded (unless suction pressure is higher than
varipower equation and forced compressor to be in
4 cylinders). Note suction pressure.
2. Increase setpoint slowly to until unloader valve is
energized (followed by continuity light or ohmmeter).
Verify that suction pressure rise of approximately 3
psig (0.2 bars).
NOTE
If either unloader coil energizes and the suction
pressure does not change, the unloader assembly
must be checked.
b. Solenoid coil replacement
NOTE
The coil may be removed without pumping the unit
down.
1. Disconnect leads. Lift off coil. (see Figure 4-9)