Diagnostics - Microprocessor Or Wiring; Figure 8−28 Electronic Expansion Valve; Figure 8−29 Electronic Expansion Valve; Table 8−4 Evxv Connections - Carrier VECTOR 6500 Operation & Service Manual

3
2
FLOW
DIRECTION
1. Electronic Expansion
Valve
2. Coil Boot
Figure 8−28 Electronic expansion valve
a. Diagnostics - Microprocessor or Wiring
1. Locate the wires, on the engine harness side of the
EVXV connector labeled EXVA, EXVB, EXVC,
EXVD and EXVE. These will correlate to the connec-
tor pins labeled A, B, C, D and E. Refer to Table 8−4.
Table 8−4 EVXV Connections
Connector Pin Wire Color
A ORANGE
B
C YELLOW
D BLACK
E GREY
2. Set the voltmeter to the DCV scale. Ensure the unit is
disconnected from standby power and start the unit
in Standby Operation. Wait for the MessageCenter
to display "UNIT SHUTDOWN - SEE ALARM LIST".
3. Perform the following test on the wiring coming from
the microprocessor:
Place the positive (+) voltmeter lead on pin E, the
negative (-) voltmeter lead on pin A and observe the
meter for several seconds. The voltage reading will
be very low, then rise to battery voltage (approxim-
ately 12.3VDC with a good battery) for a few
seconds, then drop back to a lower reading
4. Repeat for pins B,C and D.
5. If there is no voltage reading or if the voltage never
rises to battery voltage level, there is a problem in the
wiring or the microprocessor. Test all wiring from the
EVXV connector to the microprocessor and verify
62-11389
4
1
3. Coil
4. Five Pin
Connector
Winding
A
RED B
A
B
COM (+12V)
good continuity before replacing the micropro-
cessor.
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 07-00375-00), connect the 5
pin test cable to the valve connector, and the cable
wires to the tester in accordance with wire and termin-
al color. (if a 5 pin tester cable is required, order Carri-
er 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 se-
quentially until all four are illuminated. 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 resist-
ance between connector pin A & E, B & E, C & E and
then between D & E. In normal ambient, the resist-
ance between the pins should be 46 ohms. If an infin-
ite or zero reading is observed, the piston and drive
motor assembly is to be replaced.
c. Diagnostics - Valve
If the valve failed Pretrip and passed the pre-
ceding diagnostic testing, this is an indication
that the valve internal mechanism is damaged
and the piston and motor assembly is to be re-
placed.
PIN A (ORANGE)
A
A
PIN C (YELLOW)
Figure 8−29 Electronic Expansion Valve
1. To test the valve internal mechanism, install a mani-
fold gauge set on the suction service valve and a
stepper motor drive tester. Refer to Section 8.8.6b.
2. Start the unit, set the step rate to 200 steps per
second (refer to Section 8.8.6 step b.) and close the
valve while watching the suction pressure. Within one
minute the suction pressure should begin to fall.
8−30
NOTE
PIN B (RED)
B
COMMON
(+12VDC)
B
PIN D (BLACK)
PIN E (GRAY)