Porsche P-80 2005, Manual

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Page 3.18
Climate Control Systems Diagnosis & Repair
Sports Cars System
Cooling Fans – Sports Cars Up To M.Y. 2004
The cooling fans promote airflow through the engine
coolant radiators and condensers to improve heat transfer
from the refrigerant to ambient air.
A ballast resistor (see graphic below) reduces voltage to
the condenser fans for first (low) speed operation. The
resistor is bypassed and the condenser fans will run at
second (high) speed when refrigerant pressure exceeds
16 bar (232 psi). This is controlled by the 3-way medium
pressure switch via the DME.
The cooling fans will run at second (high) speed when
engine coolant temperature exceeds 102° C (216° F).
Cooling Fans – Sports Cars M.Y. 2005 - on
The engine coolant radiator and condenser fan speed is
controlled by the DME and fan speed is infinitely variable.
Inputs are received by the DME for refrigerant pressure
(supplied via CAN from the A/C control unit) and engine
coolant temperature. The DME sends the fan speed
command via CAN Drive to the gateway and via CAN
Comfort to the front-end control unit.
The front-end control unit controls the cooling fans (right
and left) together via a pulse width-modulated (PWM) signal
to an output module. The output module evaluates and
processes the PWM signal and relays it to the fans.
Refrigerant Pressure vs. Fan Speed in Percent
Coolant Temperature vs. Fan Speed in Percent
Notes: