C3 Check Return Air Sensor
electrical
Description
Compartment 3 return air sensor is out of range, and in perishable mode compartment 3 shuts down; in frozen mode it runs reduced capacity cool.
Activation Conditions
Compartment 3 Return Temperature Sensor (RAT) is not within the range of -53 to +158°F (- 47 to +70° C).
Unit Behavior
Engine and Electric Operation: If setpoint is in the perishable range, compartment 3 will shutdown. If setpoint is in the frozen range, compartment 3 will run in reduced capacity cool.
Reset Conditions
Auto reset when 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 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.