BMW 520i car radiator auxiliary electronic fan does not turn, air conditioning blower does not work failure. But the air conditioning control panel shows normal, the compressor can work properly.
    The driver's failure to verify the above. And then use the car Boshi A2600j detection, read the fault code for the 25 - parking wake-up signal is bad (heating "REST"), and the fault code can not be cleared. Numerical analysis, air conditioning system, the sensor values ​​are normal. As the car air conditioning control panel without "REST" hotkey, so temporarily ignore the fault code.
    Auxiliary radiator The electronic fan is located in front of the tank, and the electronic fan consists of a fan motor module and a fan motor. Engine computer DME according to the radiator outlet temperature sensor signal and air conditioning pressure signal, the output frequency of 10-100Hz signal control auxiliary radiator fan ground to FM signal to change the electronic fan speed, fan speed with cooling water temperature and air conditioning pressure and Increased and increased, and as the speed of the vehicle increased and decreased. With a multimeter to detect the electronic fan power and ground line are normal, connected to the air conditioning pressure gauge, open the air conditioning, then with the air conditioning pressure increases, the oscilloscope display output frequency also increased, that is, the value of 10-100Hz changes. Which can determine the air conditioning OK, you can implement the electronic fan motor module is bad. Replace the electronic fan, the electronic fan to work properly.
    2000 BMW 520i air conditioning system uses CAN-BUS control technology, such as air conditioning IHKA computer and instrument IKE computer communication between the signal using K-BUS line transmission, IHKA air conditioning between the wind direction control motor M-BUS line transmission. Blower control is the air conditioning computer to a linear voltage signal output to the blower amplifier to achieve the blower speed changes. Blower power can be increased through the air conditioning panel, the control voltage linear increase, the blower speed also increases. Power amplifier located in the air conditioner bellows on the right, there are 5 lines, respectively, 12V power cord, ground wire, A / C computer control signal line, the other two lines to the blower motor. Signal line in the 2.1V-7.2V between the change, the voltage is 2.1V when the lowest blower, the signal voltage is greater than 7.2V when the most high-end, full-speed blower blower. The measured signal voltage changes normally and the amplifier has no output voltage to the blower. Unplug the blower controller cable and plug the plug again, and the blower is working properly. Repeated tests, the blower can work properly. It can be seen that the blower controller plug is in poor contact.
    After re-welding, the installation method, air conditioning system work well, troubleshooting.
    Why will the line connected with the C13 burn it? After the user asked in detail, because the battery serious loss of power, the driver did not remove the battery is positive and negative connection, the battery on the car charging, because the charging current is too large, resulting in air conditioning control unit The line is blown. Therefore, for electric control cars, do not charge the battery on the car, otherwise it will burn out the electronic control unit. As the removal of the battery is positive and negative wiring, will make the memory of the control unit disappeared, especially for vehicles with audio anti-theft system, but also lead to audio lock code. To prevent accidents, before removing the battery charge, you should first connect a battery.