A/C power output DDE 5.0

The A/C compressor is switched on and off by the DDE control unit via the A/C compressor relay. The DDE control unit receives a request via the CAN bus from the heating and air conditioning control unit to switch on the air conditioning compressor.

If a request to switch on the air conditioning compressor is received, the DDE control unit checks whether there are conditions prevailing that do not allow the compressor to be switched on. The DDE control unit then switches the air conditioning compressor relay on or off accordingly. Switch-on of the A/C compressor is inhibited by the DDE control unit under following conditions:

• Start-off status:
  Road speed < 9 km/h AND
  Accelerator pedal > 31 % AND
  Engine speed < 1750 rpm
  
• Coolant temperature > 118 °C
  
• Throttle dip:
  Engine speed < 660 rpm
  
• while starting
  
• one of the following faults stored on the DDE:
  
  • 3F10, 3F20, Pedal position sensor
    
  • 3F60, Road speed signal
    
  • 4670, Supply voltage 1
    
  • 4690, Supply voltage 3
    

Troubleshooting

Control of the air conditioning compressor relay is monitored. The following faults are monitored:

• 4100, Activation short circuit to B+
  
• 4101, Activation short circuit to B-
  
• 4102, Activation circuit break
  
• 4103, Excess temperature output stage