Ventilation fan
| Ventilation fan |
The fan control unit is supplied with B+ from K1 pin 20 on the ACC unit and power grounded from grounding point G41P. The ground lead is also reference ground from K1 pin 1 on the ACC unit. The fan control unit is controlled by an analogue voltage of 0-5 V from K1 pin 13 on the ACC unit. The fan current increases as the control voltage increases.
The control module regulates the fan current in the following way:
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If the engine is stationary, 0 A is selected.
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When the starter motor engages, 0 A is selected.
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When starting in cold weather, the coolant temperature and outside temperature are determined. The lower the values, the lower the current. For conditions for cold starts, see
Cold start in auto
.
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Under normal driving conditions it is at its lowest when the current blended-air temperature corresponds with the requested temperature in both zones (none of the zones requires cooling or heating). The current is increased as soon as either of the zones requires cooling or heating.
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At higher speeds the air from outside will be forced into the car. The faster the car travels the greater the effect of the incoming air. The ACC unit calculates an air flow value based on the speed of the car, air and blending flap position.
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With manual selection of defrost or HI, 6 fan steps are shown. With selection of LO, 8 fan steps are shown which is MAX fan speed. Required fan speed can also be selected manually on the panel. If fan speed 0 is selected then the A/C will be disengaged, but otherwise the ACC system is fully active.
Fan speed is shown with a number of positions by the ACC unit knob.
| Adjustment |
With the diagnostics tool, the ACC unit can be adjusted to delay fan engagement if there is a risk of mist forming on the inside of the windscreen. This occurs if the engine has been turned off for more than 1 minute and the outside temperature is between 0°C and 15°C.
The delay period can be set to between 0 and 30 s.
| Diagnostics |
In the event of short circuit in the control circuit diagnostic trouble code B2425 is generated.
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