8-33 62-11039
CAUTION
The +5.0 VDC (terminal B) is common between the Compressor Discharge Pressure T ransducer, the
Compressor Suction Pressure Transducer, and the RPM sensor. If this circuit is shorted to ground
(due to one of the mentioned components being defective or a worn wire) the MessageCenter will
show:
Suction Pressure: --14.7 psig (--1 Bar)
Discharge Pressure: 0 PSIG/Bar
Engine RPM: 0.
8.21.3 Replacing Compressor Suction Pressure
T ransducer
a. Pump down compressor until the suction pressure is
approximately 0--5 PSIG (0--.4 Bar). (Refer to Sec-
tion 8.10.1.)
b. Disconnect wiring from defective transducer. Slowly
remove the transducer. The pressure remaining in
the suction line will be held in place by a Schrader
valve located inside the fitting. The CSP is located on
the suction line just above the Suction Service Valve.
(See Figure 2-2).
c. Install new suction transducer, being careful to obtain
the correct transducer for your unit. R-404A CSPs
have a blue dot on the side. Check for leaks.
d. Open the King Valve and check operation.
e. Evacuate and dehydrate the compressor. (Refer to
Section 8.12.)
f. Check unit operation by running pretrip (Refer to Sec-
tion 3.5).
8.22 REPLACING RECEIVER SIGHT GLASS AS-
SEMBLY
NOTE
Place unit in Service Mode before performing
the following operations. Refer to Section
5.2.3.
a. Store the refrigerant in an evacuated container. (Re-
fer to Section 8.10.1.)
b. Unscrew the sight glass assembly. Wrap threads
with teflon tape or spread some sealing compound
on pipe threads of new sight glass assembly or plug
and install. The torque value for the sight glass as-
sembly is 37--44 ft--lbs (5.1 to 6.1 Mkg)
c. Leak check receiver sight glass Section 8.11.
d. After leak checking unit, evacuate and dehydrate as
outlined in Section 8.11.
e. Add refrigerant charge. (Refer to Section 8.12.4)
f. Check unit operation by running Pretrip.
8.23 COMPRESSOR SUCTION MODULATION
VALVE (CSMV)
The purpose of the SMV is to control suction pressure,
maintain the compressor within its operating envelope,
and maximize unit capacity and fuel economy.
At initial startup, the microprocessor will go through a
self test. When the test is complete, the
MessageCenter will display “SMV CLOSING”. The
process of fully closing the SMV on startup is known as
“homing” the SMV. When homing is complete, the
MessageCenter will display “SETTING SMV XX%”. The
XX% will count up to a predetermined percentage
depending on ambient temperature and box
temperature. The unit will then go through its normal
start procedure.
2-1/8 inch Nut
CSMV
Figure 8 --34 Suction modulation valve (CSMV)
8.23.1 Function
The SMV coil consists of two windings labeled 1 and 2.
Each winding has two poles, labeled A and B.
Both poles of both windings have a wire connected back
to the micro.
Looking at the 4--pin connector on the SMV coil, the
wiring is as follow :
Table 8 -7. CSMV Connections
Connector Pin Wire Color Winding/Pole
A BLACK 1A
B WHITE 1B
C RED 2B
D GREEN 2A
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