A/C power output DDE 4.0

The A/C compressor is switched on and off by the DDE control unit. The DDE control unit receives a message from the heating and A/C control unit as to whether the air conditioning system button is pressed and whether the heating and A/C control unit is requesting that the compressor be switched on. If a request is received to switch on the A/C compressor, the DDE control unit checks whether conditions that do not permit the compressor to be switched on apply and sends a corresponding message back to the heating and air conditioning control unit. Switch-on of the A/C compressor is inhibited by the DDE control unit under following conditions:

• Start-off status:
  Road speed < 10 km/h AND
  Accelerator pedal > 60 % AND
  Engine speed < 1800 rpm
  
• Acceleration:
  Accelerator pedal change > 400%/second AND
  Engine speed < 3000 rpm
  
• Coolant temperature > 117°C
  
• Throttle dip:
  Engine speed < 650 rpm
  
• while starting
  
• Fault code stored in DDE:
  Fault code 500 ”Road speed signal” OR
  Fault code 120, 220 ”Pedal position sensor”
  

Troubleshooting

The line between the DDE control unit and heating and air conditioning control unit is monitored for short-circuit and open circuit. Fault code 3515 ”A/C power output” is stored in the case of defect.