Check Air Supply Sensor
electrical
Description
Supply Air Temperature Sensor is out of -53 to +158°F (-47 to +70° C); the unit alarms and switches to return air control, or enters Cargo Protect mode with 00122 active.
Activation Conditions
Supply Air Temperature Sensor (SAT) is not within range of -53 to +158°F (-47 to +70° C).
Unit Behavior
If Alarm 00122 Check Return Air Sensor (RAT) is not active, Functional Parameter Temperature Control is set for Supply Air and setpoint is in perishable range: Alarm and switch to return air control. If Alarm 00122 Check Return Air Sensor (RAT) is active, alarm and system will enter Cargo Protect mode. Refer to 4.11.1.
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 and then back on again.
Corrective Actions
1. Check Sensor a. Inspect sensor and connectors. Verify that there is no damage to sensor, and no damage, moisture or corrosion in connectors. b. Check sensor resistance. Refer to Note 3 in Section 7.2. 10,000 Ohms @ 77°F (25°C). Refer to Section 8.9.16 for chart of resistances for different sensors. 2. Check Sensor Wiring a. Inspect connector pins and terminals at sensor connector 1-3MSM-4 and 16 (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 the sensor.