Carrier VECTOR 1550 Series Operation & Service Manual page 235

Diagnostics - Stepper Motor
The valve stepper motor may be tested using a step-
per motor drive tester or ohmmeter.
a. 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 ca-
ble wires to the tester in accordance with wire and
terminal color. (if a 5 pin tester cable is required, or-
der Carrier Transicold part number 07-00375-11
b. 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 illuminated. Any LED
failing to illuminate indicates an open on that leg and
a need to replace the drive.
c. To test with an ohmmeter, check the winding re-
sistance between connector pin A & E, B & E, C & E
and then between D & E. In normal ambient, the re-
sistance 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.
Diagnostics - Valve
If the valve failed pretest 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
replaced.
PIN A (ORANGE)
A
COMMON
(+12VDC)
A
PIN C (YELLOW)
PIN E (GRAY)
Figure 8-17. Electronic Expansion Valve
NOTE
PIN B (RED)
B
B
PIN D (BLACK)
a. To test the valve internal mechanism, connect a
gage to the suction service valve and a stepper mo-
tor drive tester.
The scroll compressor achieves low suc-
tion pressure very quickly. Do not use the
compressor to evacuate the system below
0 psig. Never operate the compressor with
the suction or discharge service valves
closed (frontseated). Internal damage will
result from operating the compressor in a
deep vacuum.
b. Start the unit, set the step rate to 200 steps per
second and close the valve while watching the suc-
tion pressure. Within one minute the suction pres-
sure should begin to fall.
c. 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.
Replacing Expansion Valve & Screen
a. Remove the refrigerant charge. (Refer to section
8.5.1).
b. Remove coil and unbraze valve. Clean all tube
stubs so new valve fits on easily.
c. Use a wet rag to keep the replacement valve cool
and braze in place.
d. Leak check, evacuate the unit and charge in ac-
cordance with sections 8.5.2, 8.5.3 & 8.5.4.
8-23
CAUTION
62-61753-21