8–43 62-12259
Figure 8.27 Evaporator Expansion Valve Pins
8.8.8.3 Diagnostics - Valve
If the valve failed Pretrip and passed the preceding diagnostic testing, this is an indication that the valve
internal mechanism is damaged and the piston and motor assembly is to be replaced.
Test the EVXV valve internal mechanism
1. Install a manifold gauge set on the suction service valve and a stepper motor drive tester. Refer to Section
8.6.1.
NOTICE
The scroll compressor achieves low suction 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.
2. Start the unit, set the step rate to 150 steps per second, open and close the valve while watching the suction
pressure. 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.
Test the ECXV valve internal mechanism:
1. To test the ECXV, install a stepper motor drive tester to the valve, refer to Section 8.8.7.
2. Use the stepper motor drive tester to close the ECXV completely, and run the unit for five minutes.
3. Check for a temperature change through the valve. If there is a temperature change, it indicates that the
ECXV is stuck open and needs to be replaced. If there is not a temperature change, record the CDT and AC
current from Unit Data.
4. Use the stepper motor drive tester to open the ECXV, and run the unit for five minutes.
5. Check for a temperature change through the valve, if there is a temperature change, it indicates that the
ECXV opened correctly.
6. From Unit Data, make sure the CDT temperature reading went down, and that the AC current draw went up.
A
B
B
A
PIN A (ORANGE)
PIN B (RED)
PIN C (YELLOW)
PIN E (GRAY)
PIN D (BLACK)
COMMON
(+12VDC)
To Next Page