Thermo King 002008, Manual

Page: 83 / 155

Refrigeration Maintenance
83
3. Raise the discharge pressure of the
compressor first by blocking the condenser
coil air flow by covering the roadside
condenser grille with apiece of cardboard. If
this does not raise the discharge pressure to
the cutout level of the HPCO, increase the
engine speed by overriding the throttle
solenoid. This should increase the discharge
pressure enough to cause the HPCO to cut out.
The cut out pressure should be 470 ± 7 psig
(3241 ± 48 kPa).
4. If the HPCO does not open to de-energize the
fuel solenoid and stop the engine, it must be
replaced.
High Pressure Switch (HPSW)
Test
The high pressure switch (HPSW) is located on
the compressor discharge manifold. This switch is
used by the microprocessor to confirm the
operation of the receiver tank pressure solenoid
and the purge valve. It is connected to the 7K1
and HP wires in the main wire harness. The
HPSW opens when the discharge pressure rises
above 300 psig (2068 kPa). The HPSW closes
when the discharge pressure drops below 200 psig
(1379 kPa).
Use the following procedure to test the HPSW:
1. Install a gauge manifold on the compressor.
2. Disconnect the HPSW from the 7K1 and HP
wires in the main wire harness.
3. Check the HPSW for continuity. It should be
closed when the unit is not running.
4. Use the Service Test mode to run the host unit
in High Speed Cool. Refer to the appropriate
Diagnosis Manual for specific information
about the Service Test Mode.
5. Cover the condenser to raise the discharge
pressure.
6. Monitor the discharge pressure. When the
discharge pressure reaches 300 +25/-0 psig
(2068 +172/-0 kPa), the HPCI should open.
7. Uncover the condenser to lower the discharge
pressure.
8. Monitor the discharge and suction pressures.
When the discharge pressure reaches 200 ±
20 psig (1379 ± 138 kPa), the HPSW should
close.
9. Replace the HSW if it does not function
properly.
10. Reconnect the HPSW to the main wire harness
and remove the gauge manifold.
CAUTION: If the discharge pressure
reaches 477 psig (3289 kPa), shut the unit
off immediately. Do not allow the
discharge pressure to exceed 477 psig
(3289 kPa).
1. Relief Valve (66-6543)
2. O-Ring (33-1015)
3. Adapter Tee Weather Head (No. 552X3)
Figure 56: High Pressure Cutout Manifold