Check Defrost Term 2 Sensor
refrigeration
Description
Defrost Termination Temperature Sensor is out of -58 to +266°F (-50 to +130°C); the system uses SAT for defrost initiation, or RAT if 00123 is also active.
Activation Conditions
Defrost Termination Temperature Sensor (DTT) is not within the range of -58 to +266°F (-50 to +130°C).
Unit Behavior
When this alarm is active, the system will use only the SAT for defrost initiation. If both this alarm and the 00123 Check Air Supply Sensor are active the system will use the RAT for defrost initiation. In either case, defrost will be allowed when the sensor is below 45°F (7.2°C). When this alarm is active defrost will terminate when the SAT reaches 55°F (12.8°C). If both this alarm and 00123 Check Air Supply Sensor are both active, defrost will terminate after ten minutes.
Reset Conditions
Auto reset when the sensor is in range or, alarm may be manually reset using the display mounted keys or by turning the unit off, then back on again.
Corrective Actions
1. Check Sensor a. Inspect sensor and connector. Verify that there is no damage to sensor, and no damage, moisture or corrosion in connector. b. Check sensor resistance. (Refer to Note 3 in Section 7.2) 10,000 Ohms @ 77°F (25°C.) See Section 8.9.16 for complete table of temperatures and resistance values. 2. Check Sensor Wiring a. Inspect connector pins and terminals at sensor at connector 1-3MSM-3 and 26 (see wiring schematic). Verify that there is no physical damage to harness, and no damage, moisture or corrosion in connectors. b. Place the system in PC mode. Refer to Note 2 in Section 7.2. Disconnect sensor from harness. Check for 3.0 ± 0.1 VDC volts at harness plug between pins. This verifies microprocessor output and wiring connections to sensor.