Check Ambient Air Sensor
electrical
Description
Ambient Air Temperature Sensor is out of -53 to +158°F (-47° to +70° C); the unit alarms and uses 122°F (50°C) for calculations.
Activation Conditions
Ambient Air Temperature Sensor (AAT) is not within range of -53 to +158°F (-47° to +70° C).
Unit Behavior
Alarm and a value of 122°F (50°C) will be used for any calculations.
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 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). 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 and connector 1-3MSM-1 and 24 (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 at harness plug between pins. Voltage should be 3.0 ± 0.1 VDC volts at harness plug between pins. This verifies microprocessor output and wiring connections to the sensor.