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| Illustration 1 | g01912574 |
To display fault codes, depress the ON key three times in rapid succession. The digital display will then display any active fault codes. Pressing the ON key again repeatedly will scroll through any existing error codes. After five seconds without further key presses, the system will exit the diagnostics mode and return to normal operation.
No Faults - E0
Cab Sensor Shorted - E1
Cab Sensor Open - E2
Evaporator Probe Shorted - E3
Evaporator Probe Open - E4
Duct Sensor Shorted - E5
Duct Sensor Open - E6
Pressure Transducer Open - E151
Pressure Transducer Shorted - E12
Water Valve Actuator Error - E13
Electronics or Comm. Error - E17
Clutch Open - E18*
Clutch Shorted - E19*
No Refrigerant - E20*
High-pressure - E22*
Low Voltage Error - E23*
* Future implementation
The ATC Advanced Diagnostics control panel allows the technician to see real-time system information on the control panel display. Control panel display will assist in A/C-heater servicing. This real-time information can help the service technician diagnose certain system problems.
To display advanced diagnostics, depress ON key three times in rapid succession (fault codes displayed) then immediately press and hold ON key for five seconds. The text "CAB" will be displayed. After a few seconds, the real-time value of the cab temperature measured by the ATC is displayed. This value, as well as any other value displayed by the control panel, will continuously update. Pressing the ON key again repeatedly will scroll through all of the available diagnostics information
CAB - Cab Air Temperature (°C or °F)
EVAP - Evaporator Core Temperature (°C or °F)
DUCT - Duct Air Temperature (°C or °F)
HEAT - Water Valve Command (% of valve open)
A-C - A-C Clutch Request (on / off )
FAN - Blower Fan Speed (% of maximum fan speed)
DEF - Defrost Mode Active (On/Off)
HI-P - High Side Pressure (psig or bar)
PRHT - Blower Enable Active (On/Off)
VOLT - System Voltage (DC Volts)
Note: The system can be operated normally while in advanced diagnostics mode, including changing the temperature set point or changing the blower fan speed, to evaluate the response of the system.
The firmware version of the control panel and Electronic Control Unit (ECU) can be displayed. From the advanced diagnostics mode, press and hold the ON key for five seconds. The text CTRL will be displayed and after a few seconds, the control panel firmware version number will be displayed. Pressing the ON key will toggle to the ECU firmware version.
The following firmware version information is available:
CTRL - Control Panel Version
ECU - ECU Version
To exit the advanced diagnostic mode or firmware Version mode, turn the system OFF by pressing the OFF key.
- Turn on control panel with the ON key.
- Check to see if the display Illuminates.
- Verify that the control panel is plugged into the wire harness.
- Check to see if wire harness is wired into vehicle properly.
- Turn up fan with the fan UP key.
- Make sure that the fan is plugged into wire harness, verify all wiring connections.
- Verify that the circuit breakers or fuses are intact.
- If all other functions work properly, replace ECU.
- Turn up heat with the Temperature UP key. Use the advanced diagnostics to verify that the water valve is commanded open.
- Inspect and verify all wiring connections.
- Verify that any coolant shut off valves on the engine are open.
- Verify that warm coolant is flowing into the heater core by testing the heater hoses.
- Inspect and replace the electronic water valve if necessary.
- Inspect and replace ECU if necessary.
- Turn down heat with the Temperature DOWN key and enable the defrost mode. Use the advanced diagnostics to verify that the A/C clutch is requested ON.
- Verify that the system is fully charged with refrigerant.
- Verify that voltage is present at the compressor clutch.
- Verify that the correct voltage is present at the clutch relay on the wire harness.
- Inspect and verify all wiring connections.
- Inspect and replace clutch relay if necessary.
- Inspect and replace refrigerant high-pressure and/or low-pressure cut out switches if necessary.
- Inspect compressor and clutch assembly and replace clutch if necessary.
The system is not controlling the cab temperature properly
- Inspect the cab air temperature sensor.
- Verify that the recirculation vent inlet is not obstructed. Inspect and replace recirculation vent air filter if necessary.
- Inspect and replace recirculation vent air filter, if necessary.
- Change the setpoint temperature in small increments.
- Verify that the water valve is working properly. Refer "No Heat"(see No Heat).
- Verify that the compressor clutch is working properly. Refer "No Cooling".
The evaporator core is icing up and restricting airflow
- Inspect the evaporator core probe.
- Verify that the probe is making good contact with the evaporator fins and is not loosely inserted.
- Reposition the probe and check the core temperature during operation using the advanced diagnostics.
- Replace the evaporator core if necessary.