Automatic Temperature Control Troubleshooting Codes
Use this procedure to troubleshoot the performance of the HVAC system for machines equipped with automatic temperature control.
Connect Cat® Electronic Technician (Cat® ET) and check for diagnostics associated with the HVAC system. Refer to the Machine Troubleshooting Guide if any of the following codes are active.
| |
| Illustration 1 | g03090916 |
|
HVAC Diagnostic Codes | |
| |
| Illustration 2 | g06277724 |
|
Typical HVAC ET status parameters and values | |
- Diagnostic Codes
- Low-Pressure Switch / High Pressure Switch
- Low Refrigerant Charge
- Water Valve Actuator
- A/C Compressor
Connect Cat® ET to the service tool connector. Check for active diagnostic codes. Look for active codes that are related to the HVAC system in Illustration 1. Use the appropriate circuit test to troubleshoot any active codes before continuing.
Low-Pressure Switch / High Pressure Switch
Use Cat® ET to monitor the "Air Conditioning Refrigerant Monitoring Circuit" status parameter. With a proper charge the status should be closed. If the status is open, check the pressure switches and circuit (refer to the pressure switch tests section in this book).
Refer to Air Conditioning Performance - Test
Test the water value actuator control by switching to heat mode. Use Cat® ET and monitor the "Cab Air Heater Engine Coolant Actuator Duty Cycle" status parameter while rotating the temperature dial. The parameter should go to 5% when the temperature dial is full CCW and 95% when the temperature dial is full CW. If the duty cycle of the "Cab Air Heater Engine Coolant Actuator" does not change in response to the temperature dial, check the temperature dial. If the duty cycle of the "Cab Air Heater Engine Coolant Actuator" changes in response to the temperature dial, verify the water valve actuator circuit. Verify that the actuator is rotating.
Switch to AC mode and use Cat ET to monitor the "A/C Compressor" status parameter with the engine running. If the compressor status does not turn to ON after 20 seconds, check the evaporation temperature circuit. (Refer to 2357 diagnostic code in "Sensor Signal (Analog, Passive - Test")). For the pressure switch circuits, refer to the pressure switch tests section in this manual. If the compressor status is ON and the compressor does not turn on, check for power at the compressor connection.
Note: If the compressor status is on and there is power at the compressor clutch, then replace the compressor.
- Diagnostic Codes
- Water Valve Actuator
Connect Cat ET to the service tool connector. Check for active diagnostic codes. Look for active codes that are related to the HVAC system in Illustration 1. Use the appropriate circuit test to troubleshoot any active codes before continuing.
Test the water value actuator control by switching to heat mode. Use Cat® ET and monitor the duty cycle for the "Cab Air Heater Engine Coolant Actuator" status parameter while rotating the temperature dial. The parameter should go to 5% when the temperature dial is full CCW and 95% when the temperature dial is full CW. If the duty cycle for the "Cab Air Heater Engine Coolant Actuator" does not move with the temperature dial, check the temperature dial. (See the troubleshooting in the "Switch Circuits - Test" section of this manual). If the duty cycle of the "Cab Air Heater Engine Coolant Actuator" moves with the temperature dial, verify the water valve actuator circuit. Verify that the actuator is rotating.
No Airflow from Evaporator Blower Motor
Perform this test with the key in the on position. Use a 5P-7277 Voltage Tester or use a 257-9140 Digital Multimeter and connect the negative probe to the pin 7 wire on the control panel using a 7X-1710 Multimeter Probe or equivalent. Check the supply voltage first by connecting the positive probe to the pin 1 wire using a 7X-1710 Multimeter Probe or equivalent. If the system voltage is not measured, do not perform any of the other tests below until that is repaired. Set the blower switch to low speed. Connect the positive probe to pin 5 using a 7X-1710 Multimeter Probe or equivalent. Record the voltage. For a properly working control panel the voltage should be the same as the system voltage. Repeat for all speeds. Replace the panel if any of the voltages are not present during the test. If the panel passes the test, then refer to the machine electrical schematic and check for voltage to the motor and resistor.
| |
| Illustration 3 | g03543997 |
|
With Brushless Motor - 361-5586 Blower Assembly | |
| |
| Illustration 4 | g03543998 |
Perform this test with the key in the on position. Connect Cat ET and look for diagnostics relating to the control panel (2811-3, 2811-4). Use the following procedure to troubleshoot the diagnostics.
Use a 5P-7277 Voltage Tester or use a 257-9140 Digital Multimeter and connect the negative probe to the pin 6 wire on the control panel using a 7X-1710 Multimeter Probe wire assembly or equivalent and connect the positive probe to the pin 4 wire. Rotate the dial and observe the voltage reading, the voltage should vary between 2 to 4.5 V for a properly working panel.
If the panel passes the test, then refer to the machine troubleshooting guide and check for voltage to the motor and driver module if equipped.