TUBE (INLET) 4W0940 - Caterpillar

Problem: No Cool Air Is Provided, But Blower Is Functional.
Check the engagement of the compressor clutch without the engine running.
Put the air conditioning system in the "AUT" mode.
Manually override the system by pressing the air conditioning override switch (3) .Note: There is a 15 second delay between the time that the air conditioning override switch (3) is pressed and the clutch egages.Expected Result: The clutch engages.Results:
OK - Proceed to step 2.
NOT OK - Proceed to step 3 if the clutch does not engage.
Put the air conditioning system in the "AUT" mode and press the (decrease) temperature selection switch (5) until the lowest setting is displayed.Note: The ambient temperature must be higher than the lowest setting.Expected Result: The clutch engages.Results:
OK - A refrigerant problem exists. Refer to Sevice Manual, SENR5664, "Air Conditioning and Heating Systems With R-134a Refrigerant".
NOT OK - Proceed to step 3 if the clutch does not engage.
Check for voltage (24V) at the compressor clutch coil on wire 513-OR.Expected Result: Voltage is present.Results:
OK - Proceed to step 4.
NOT OK - Proceed to step 7 if voltage is not present.
Check the coil resistance of the compressor clutch. At 20°C (68°F), the coil resistance will be between 13 and 19 ohms.Expected Result: The coil resistance is good.Results:
OK - Repair or replace the wiring harness ground, 200-BK, circuit as required.
NOT OK - Replace the compressor if the resistance is not good.
Check for voltage (24V) at the a/c HI/LOW pressure switch on wire 519-PK.Expected Result: Voltage is present.Results:
OK - Replace the a/c HI/LOW pressure switch.
NOT OK - Proceed to step 6 if voltage is not present.
Check the evaporator sensor. Refer to Testing and Adjusting, "Temperature Sensor - Test".Expected Result: The sensor is not good.Results:
OK - Replace the sensor if the sensor is not good.
NOT OK - Proceed to step 7 if the sensor is good.
Check the sensor in the cab. Refer to Testing and Adjusting, "Temperature Sensor - Test".Expected Result: The sensor is not good.Results:
OK - Replace the sensor if the sensor is not good.
NOT OK - Proceed to step 8 if the sensor is good.
Check for voltage (24V) at the a/c relay. Refer to the section called "Relay Check" in Testing and Adjusting, "Troubleshooting Air Conditioner Control".Problem: One Or More Blower Speeds Do Not Work.
Set the desired fan speed on the preset temperature display.
Check for voltage (24V) at the blower resistor.
Refer to Testing and Adjusting, "Air Conditioning System Schematic" for correct wire identification.Expected Result: Voltage is present.Results:
OK - Replace the resistor.
NOT OK - Proceed to step 2 if voltage is not present.
Check for voltage (24V) at the relay on wire 124-GN. Refer to the section called "Relay Check" in Testing and Adjusting, "Troubleshooting Air Conditioner Control".Problem: Air Does Not Come Out Of The Upper Air Towers For (Upper Body) Discharge When The Control Panel Displays The (Upper Body) Mode.
Illustration 2 g00318906
(6) Preset temperature display (10) Air inlet selection switch (FRESH AIR) (11) Air inlet selection switch (RECIRCULATE) (13) Air outlet selection switch (Under Seat) (15) Air outlet selection switch (Upper Body)
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