Dakota Quad Cab 2WD V8-5.9L VIN Z LDC (2002)
Ambient Temperature Sensor / Switch HVAC: Testing and Inspection
AMBIENT TEMPERATURE SENSOR
The thermometer function is supported by the ambient temperature sensor, a wiring circuit, and a portion of the HVAC control. If any portion of the
ambient temperature sensor circuit fails or if PCI Bus information is missing, a (- -) will appear in the display in place of the temperature, when the
sensor is exposed to temperatures above 55 °C (140 °F), or if the sensor circuit is shorted. A (- -) will appear in the display in place of the
temperature, when the sensor is exposed to temperatures below - 40 °C (- 40 °F), or if the sensor circuit is open.
The ambient temperature sensor circuit can also be diagnosed using the following Sensor Test, and Sensor Circuit Test. If the temperature sensor and
circuit are confirmed to be OK, but the temperature display is inoperative or incorrect, refer to Diagnosis and Testing the Compass Mini-Trip
Computer.
SENSOR TEST
1. Turn the ignition OFF. Disconnect and isolate the battery negative cable.
2. Disconnect the ATS harness connector.
3. Measure the resistance of the ATS using the following min/max values:
TEMPERATURE ............................................................................................................................................................. SENSOR RESISTANCE
- 40 °C (- 40 °F) ..................................................................................................................................................................................... 336 Kilohms
0 °C (32 °F) ............................................................................................................................................................................. 29.33 - 35.99 Kilohms
10 °C (50 °F) ........................................................................................................................................................................... 17.99 - 21.81 Kilohms
20 °C (68 °F) ........................................................................................................................................................................... 11.37 - 13.61 Kilohms
25 °C (77 °F) ............................................................................................................................................................................. 9.12 - 10.86 Kilohms
30 °C (86 °F) ............................................................................................................................................................................... 7.37 - 8.75 Kilohms
40 °C (104 °F) ............................................................................................................................................................................. 4.90 - 5.75 Kilohms
55 °C (140 °F) ..................................................................................................................................................................................... 2.488 Kilohms
The sensor resistance should read between these min/max values. If the resistance values are OK, refer to Sensor Circuit Test. If the resistance values
are not OK, replace the sensor.
SENSOR CIRCUIT TEST
1. Turn the ignition switch to the OFF position. Disconnect and isolate the battery negative cable. Disconnect the ambient temperature sensor wire
harness connector and the HVAC control harness connector.
2. Connect a jumper wire between the two terminals in the body half of the ambient temperature sensor harness connector.
3. Check for continuity between the sensor return circuit and the ambient temperature sensor signal circuit cavities of the HVAC control harness
connector. There should be continuity If OK, go to Step 4.If not OK, repair the open sensor return circuit or ambient temperature sensor signal
circuit to the ambient temperature sensor as required.
4. Check for continuity between the ambient temperature sensor signal circuit cavity of the HVAC control harness connector and a good ground.
There should be no continuity. If OK, refer to Diagnosis and Testing of the Compass Mini-Trip Computer. If not OK, repair the shorted ambient
temperature sensor signal circuit as required.
