9-3 SE Hatchback (9400) L4-2.0L Turbo (B205) HO (2000)
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A number of conditions must be fulfilled for the A/C relay to be grounded and the A/C compressor's electromagnetic clutch to operate.
In AUTO mode, the ACC unit will request the DICE for A/C engagement if:
-
The outdoor temperature (information via bus from the SID) is above 0 °C.
The DICE then requests the Trionic control module to ground the A/C relay if the following conditions are fulfilled:
1
The engine coolant temperature (bus information from the Trionic) is below 125 °C.
2
Refrigerant pressure (own sensor) on the high-pressure side is between 2 and 27 bar.
3
The temperature in the evaporator (own sensor) must meet the following conditions:
a
If the evaporator temperature is higher then 3 °C, the DICE will send via the bus an A/C engagement request to the Trionic control module.
b
If the evaporator temperature is below 0 °, the A/C compressor can only be switched on if points 4 and 5 are fulfilled.
4
The outside temperature (bus information from the SID) must be above 25 °C.
5
One of the following conditions must also be met:
a
The engine must have been running for less than 30 minutes (bus information from the Trionic control module).
b
Vehicle speed is below 5 km/h (bus information from the MIU).
The Trionic T7 then activates the compressor relay.
Diagnostics
In the event of a fault in any of the aforementioned sensors in the systems concerned, the A/C compressor will not work. The function chain clearly
shows the importance of obtaining diagnostic trouble code readouts from all systems because several systems are involved in any given function.
If there are no diagnostic codes with the symptom description "A/C not cooling", all the input values that can block the function must be gone through
methodically with the read values command on the diagnostic tool. The compressor relay is activated in the Trionic. Then perform fault diagnosis on the
system that "owns" the sensor or actuator that is faulty.
3. A/C, cars with Trionic T5 or Motronic engine management system
