ECU sends PWM signal to fan control unit depending on the fan speed required. If the fan is constantly on either control unit is faulty or ECU requests fan to be on possibly because of wrong temperature reading.
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Currently 8less
2011 Q7 S Line 3.0TDI, 2016 Tesla Model S 90D
8 history:
2006 A8 Sport 4.2TDI quattro SOLD,
1997 S8, reached end of life with gearbox failure
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