7–7 62-12259
00013 High Discharge Pressure
• ACTIVATION: Compressor discharge pressure switch (HPS) contacts are open. HPS contacts open
when the discharge pressure rises. Refer to Section 2.9.
• UNIT CONTROL: Engine Operation: Engine and unit shutdown and alarm.
Electric Operation: Refrigeration system shutdown and alarm with PSCON still
energized. CSMV at 50% and EVXV controls superheat.
• RESET CONDITION: Auto reset after 15 minutes if the compressor discharge pressure falls below limit,
or alarm may be manually reset using the display mounted keys or by turning the unit off, then back on
again.
NOTE
Follow the steps below until a problem is found. Once a repair or correction has been made, the
active alarm should clear itself (refer to reset condition above). Operate the unit through the appro-
priate modes to see if any active alarm occurs. Continue with the steps below as necessary.
Corrective Actions:
1. Check System Pressures - Install manifold gauge set and check and compare compressor discharge
and suction pressures with those shown in Unit Data. Refer to Section 8.8.11 for instruction on compari-
son. If discharge pressure is in normal range, proceed to step 5.
2. Check Airflow Through Radiator and Condenser Coil
a. Inspect condenser and radiator. Ninety percent or more of the coil surface must be undamaged.
Condenser/Radiator coil must be clean.
b. Check airflow (with unit running). Verify even airflow through the entire coil, and no “dead” spots.
c. Check condenser fan rotation / operation. Fans should operate correctly. Air should be directed in
through the grill, and into the engine compartment.
3. Perform Pretrip - Check CSMV and ECXV tests. Refer to Section 3.7. Pass Test.
4. Check Refrigerant Charge - Refer to Section 8.6.2. Charge must be correct.
5. Check HPS Power And Wiring
a. Inspect switch, connector pins and terminals. Verify that there is no physical damage to the switch.
Check the connections for damage and corrosion.
b.
Check for power from 1-2MSM-16 to PM-22.
If a minimum of 11 VDC is not present, check
connectors and wiring between terminals for damage, moisture or corrosion.
c.
Check continuity from HPS-B to PM-22 and HPS-A to OGF-S+. If both are good, replace
HPS.
If good continuity is not present, check connectors and wiring between terminals for damage,
moisture or corrosion.
6. Check HPS
a. With discharge pressure below the switch closing pressure (refer to Section 2.9), check continuity
from
HPS-A to PM-22. If there is no continuity replace the switch.
b. Check switch operation. Test switch. Refer to Section 8.8.10 step b.
7. Refer to Refrigeration Troubleshooting - Refer to Section 9.4. Discharge must be in range for the cur-
rent ambient and refrigerated compartment conditions.
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