Carrier Transicold X4 7300, Operation & Service Manual

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8–41 62-11637
2. Set the voltmeter to the DCV scale. Place the
START/RUN − OFF switch in the OFF position
and disconnect the starter motor wire at the
weather tight connector. Place the START/
RUN
− OFF switch back in the START/RUN posi-
tion. After three start attempts the MessageCen-
ter will display the
00031 FAILED TO START -
AUTO MODE alarm.
3. Perform the following test on the wiring coming
from the microprocessor: Place the positive (+)
voltmeter lead on pin E, the negative (
− ) voltme-
ter lead on pin A and observe the meter for sev-
eral seconds. The voltage reading will be
approximately 7.3 or 12.5 VDC depending on
valve position.
4. Leave the positive (+) voltmeter lead on pin E
and repeat for pins B, C and D.
5. If there is no voltage reading or if the voltage
never rises to the 7.3 or 12.5 voltage level, there
is a problem in the wiring or the microprocessor.
Place the START/RUN
− OFF switch in the OFF
position and reconnect the starter wire. Test all
wiring from the EVXV connector to the micropro-
cessor and verify good continuity before replac-
ing the microprocessor.
b. Diagnostics − Stepper Motor
The valve stepper motor may be tested using a stepper
motor drive tester or ohmmeter.
1. To test with a stepper motor drive tester (Carrier
Transicold part number 07 − 00375 − 00SV), con-
nect the 5 pin test cable to the valve connector
(see
Figure 8.37 ), and the cable wires to the
tester in accordance with wire and terminal
color. (if a 5 pin tester cable is required, order
Carrier Transicold part number 07
− 00375 − 11.)
2. Set the step rate to 50 steps per second and
either open or close the valve. Each red LED
should light sequentially until all four are illumi-
nated. Any LED failing to illuminate indicates an
open on that leg and a need to replace the drive.
3. To test with an ohmmeter, check the winding
resistance between connector pin A & E, B & E,
C & E and then between D & E. In normal ambi-
ent, the resistance between the pins should be
46 ohms. If an infinite or zero reading is
observed, the piston and drive motor assembly
is to be replaced.
c. Diagnostics − Valve
NOTE
If the valve failed Pretrip and passed the pre-
ceding diagnostic testing, this is an indica-
tion that the valve internal mechanism is
damaged and the piston and motor assem-
bly is to be replaced.
Figure 8.37 Evaporator Expansion Valve
1. To test the valve internal mechanism, install a
manifold gauge set on the suction service valve
and a stepper motor drive tester. Refer to
Sec-
tion 8.7.1 .
2. Start the unit, set the step rate to 200 steps per
second (refer to the preceding step b.) and
close the valve while watching the suction pres-
sure. Within one minute the suction pressure
should begin to fall.
3. If the suction pressure does not change, this is
an indication the valve is stuck and the piston
and drive motor assembly is to be replaced.
d. Replacing Expansion Valve & Screen
1. Pump down the low side. (Refer to Section
8.7.2 ).
2. Remove coil and unbraze valve. Clean all tube
stubs so new valve fits on easily.
3. Use a wet rag to keep the replacement valve
cool and braze in place.
4. Leak check and evacuate the low side. Refer to
Section 8.7.3 and 8.7.4 .
Table 8–2 EVXV Connections
Connector Pin Wire Color Winding
A ORANGE A
B RED B
C YELLOW A
D BLACK B
E GREY COM (+12V)
A
B
B
A
PIN A (ORANGE)
PIN B (RED)
PIN C (YELLOW)
PIN E (GRAY)
PIN D (BLACK)
COMMON
(+12VDC)