C2 Check Defrost Termination 1Temperature Sensor
refrigeration
Description
Compartment 2 defrost termination temperature sensor is out of range, and the unit alarms and initiates defrost based on the return air sensor condition.
Activation Conditions
Defrost Termination Temperature Sensor for Compartment 2, (2DTT) is not within the range of -53° to +158°F (-47° to +70° C.)
Unit Behavior
Engine and Electric Operation: If Alarm 00137 C2 Check Return Air Sensor C2 CHECK RETURN AIR SENSOR is not active: alarm and initiate defrost if 1RAT is below 455F (7.25C). If Alarm 00137 C2 Check Return Air Sensor is also active: alarm and initiate defrost if 1SAT is below 455F (7.25C). Under both of the above conditions, defrost will end after 10 minutes. If Alarms 00137 C2 Check Return Air Sensor and 00136 C2 Check Supply Air Temperature are also both active: alarm and defrost will not be allowed.
Reset Conditions
Auto Reset when 2DTT is in range or, alarm may be manually reset via keypad or by turning the unit off, then back on again.
Corrective Actions
1. Check Sensor a. Inspect sensors and connectors. Verify no damage to sensors, and no damage, moisture, or corrosion in connectors. b. Check sensor resistance. (Refer to Note 3 in Notes Section.) 10,000 Ohms @ 77°F (25°C). Refer to Table 8–3 for chart of resistances for different sensors. 2. Check Sensor Wiring a. Inspect connector pins and terminals at sensor and connector. Verify no physical damage to harness. Verify no damage, moisture, or corrosion in connectors. b. Place the system in PC mode, refer to Section 5.3.2. Refer to Note 2 in Notes Section. Disconnect sensor from harness. Check for 3.0 ± 0.1 VDC at harness plug between pins. Voltage should be 3.0 ± 0.1 VDC at harness plug between pins. This verifies microprocessor output and wiring connections to the sensor.