What causes the BMW 740's electric fan to continuously run at high speed?

[ClaraMarie]

Possible causes include excessively high coolant temperature, excessively high transmission oil temperature, excessively high air conditioning pressure, damaged air conditioning pressure sensor; issues with the wiring from the sensor to the JBE; internal damage to the electronic junction box (JBE) causing false reporting of air conditioning pressure. Speed principle: If the engine temperature remains within a relatively low range, the fan speed will naturally decrease. If the engine temperature consistently stays within a higher range, the fan speed will increase. It is necessary to check the relationship between engine temperature and fan speed. If it follows the above sequence, there should be no problem; if not, further inspection is required. Cooling system: The function of the automobile cooling system is to maintain the vehicle within an appropriate temperature range under all operating conditions. It consists of the cooling fan, expansion tank, thermostat, water jackets in the engine block and cylinder head, and related components.