308C CR, 314C CR and 321C CR Excavators Air Conditioning and Heating Caterpillar

Recirculation Air Sensor

Illustration 1	g01284768
Partial electrical schematic (1) Connector (2) Recirculation Air Sensor (3) Terminal 8 (4) Terminal 9

Diagnostics

Disconnect connector (1). Measure the resistance between terminal 8 (3) and terminal 9 (4). If the resistance is approximately the values that are given in the following table, the sensor is good.

If the resistance is different, the sensor is bad. Replace the sensor.

Sunlight Sensor

Illustration 2	g01285823
Partial electrical schematic (1) Sunlight sensor (2) Connector (3) Terminal 10 (4) Terminal 11

Diagnostics

Connect positive tester bar to the Y/W terminal (3) and the negative tester bar to the Y/G terminal (4) and make sure that the voltage is the following:

• The upper surface of the sensor is exposed to solar radiation: 0.3 V approximate

• The upper surface of the sensor is not exposed to the solar radiation because the sensor is covered with the hand: 0 V approximate

Note: Perform the test while the main power switch or the auto control switch on the control panel is pushed in order to operate the heater. Perform the test while the connector for the solar radiation sensor is connected to a harness. It is impossible to make sure of the variation in the voltage with a flashlight or a fluorescent light.

Fresh Air Sensor

Illustration 3	g01285851
Partial electrical schematic (1) Fresh air sensor (2) Connector (3) Terminal 12 (4) Terminal 13

Disconnect connector (2). Measure the resistance between terminal 12 (3) and terminal 13 (4). If the resistance is approximately the values that are given in the following table, the sensor is good.

If the resistance is different, the sensor is bad. Replace the sensor.

Water Temperature Sensor

Illustration 4	g01285907
Partial electrical schematic (1) Connector (2) Water temperature sensor (3) Terminal 14 (4) Terminal 15

Diagnostics

Disconnect connector (1). Measure the resistance between terminal 14 (3) and terminal 15 (4). If the resistance is approximately the values that are given in the following table, the sensor is good.

If the resistance is different, the sensor is bad. Replace the sensor.

Evaporator Sensor

Illustration 5	g01285958
Partial electrical schematic (1) Connector (2) Evaporator sensor Frost (3) Terminal 16 (4) Terminal 17

Diagnostics

Disconnect connector (1). Measure the resistance between terminal 16 (3) and terminal 17 (4). If the resistance is approximately the values that are given in the following table, the sensor is good.