Carrier 69NT40-541-001 Operation And Service page 116

b. Checking with SMA-12 portable stepper drive tester
The SMA-12 portable stepper drive tester (Carrier Transicold P/N 07-00375-00) is a battery operated stepper drive
which will open and close the SMV, which allows a more thorough check of the motor.
To check operation:
1. Stop the unit, disconnect the four pin connector from the stepper module to the valve (see
attach the SMA-12 stepper drive to the connector going to the valve.
2. Set the SMA-12 pulse per second (PPS) to one PPS and either open or close valve. Each LED should light
sequentially until all four are lit. Any LED failing to light indicates an open on that leg which indicates a poor
connection or an open coil. Repair or replace as required to achieve proper operation.
3. Restart unit, set the step rate to 200 PPS on SMA-12 for the valve, and close stepper valve while watching
the suction gauge. Within one minute the suction pressure will go into a vacuum. This is an indication that
the valve is moving.
4. If no change in suction pressure is detected, check for resistance (refer to
nections for proper continuity and retest. If the valve is functioning and all connections and motor resistance
are good, check the drive module. (Refer to
5. If the valve is determined as faulty after completing the above steps, perform a low side pump down.
Remove valve powerhead assembly, and replace with a NEW valve powerhead assembly, torque nut to 35
ft-lb, evacuate low side, and open all service valves.
DO NOT disassemble piston from NEW suction modulating valve powerhead assembly. Doing
so may result in damage to piston.
7.18.3 Checking The Controller
a. Turn unit OFF.
b. With voltmeter set to read 20 volts DC, attach the positive lead to MC1 of the four pin connector and the neg-
ative lead to the TP9. Turn ON unit, and watch the volt meter. After a short delay, the reading should remain
unchanged at 0 volts. If 5 VDC, check jumper wire form MC1 to MC8 is in place, if not, install and retest.
7.18.4 Emergency Repair Procedures:
In the event that the SMV system has a failure and replacement components are not readily available the system
can be by-passed by removing the valve piston. To remove the piston, do the following:
a. Perform a low side pump down. Refer to
b. Remove SMV powerhead by loosening the 2-1/8 inch diameter nut (see
sure and then, sliding the powerhead out.
c. Remove the piston by loosening the Allen screw and removing the piston and screw.
d. Install the powerhead assembly (without the piston), torque to 35 to 40 foot-lbs.
e. Open all valves.
f. Start the unit.
g. Adjust the suction service valve so that the approximate temperature OR current limit is maintained. For per-
ishable loads, it is recommended that the adjustment be made so that the available capacity is slightly larger
than the load, the unit will cycle OFF and ON.
h. Once repair parts become available, repair as required.
7.19 AUTOTRANSFORMER
If the unit does not start, check the following:
a. Make sure the 460 vac (yellow) power cable is plugged into the receptacle (item 3,
place.
T-316
Section 7.18.3)
WARNING
!
Section 7.4.
7–28
Figure 7.23) and
Section 7.18.2), and check con-
Figure 7.23) to relieve any pres-
Figure 5.1) and locked in