Symptom:
    Owners reflect the vehicle during the water temperature table instructions normal. But if the engine in situ, the water temperature of the pointer will slowly bias the red area. In addition, if you open the air conditioning, the phenomenon of high water temperature will gradually disappear.
    Troubleshooting:
    Check that the coolant inside the radiator is adequate. The front of the engine coupler fan looks good. Test, the engine in idle operation, open air conditioning. Air conditioning compressor pull. And the condenser in front of the electronic fan did not follow the operation. In place to accelerate a few minutes and then return to idle conditions, electronic fan began to run. Water temperature indicator has been maintained in the normal area; closed air conditioning, idle operation ten minutes later, observe the water temperature table pointer began to bias high temperature area, during which the electronic fan also has signs of operation, but no continuous operation. According to past experience, feel the fan running a lack of gear, then decided to repair work from the electronic fan control line to start. The engine has been equipped with a coupler fan, then the condenser in front of the electronic fan should be a secondary heat dissipation. Usually, the auxiliary fan is designed for air conditioning to open and the engine water temperature is too high to begin operation. BMW car design should also follow this principle.
    Turn off the ignition switch and turn it on again. Unplug the right side of the radiator 3-pin water temperature sensor plug, with a multimeter to measure, of which two pins have 12V voltage, the other one for the ride line. With a test light to the two voltage of the end of the foot one by one test. Found one of the end of the arm after the electronic fan running. The other end of the ground after the electronic fan without any reaction, which proves that the electronic fan is indeed a lack of running gear. Check the status of the electronic fan, look from the front of the bumper. Found that the fan outside the gear resistance connected to the wire there are signs of desoldering, it is estimated that this is the cause of the fault. Remove the electronic fan assembly, you can see the fan motor external line in series with two gear resistance. Measure the results of which a resistor has a terminal that has been disconnected. As the gear resistance and electronic fan is a assembly, had to buy a second-hand resistor, replace the fault after the complete elimination.
    Fault Summary:
    The chassis of the car is configured for the E39 series. The control principle of its electronic auxiliary fan is similar to the traditional design pattern we understand. In order to have a more comprehensive understanding of the system. Use the original BMW Diagnostic Instrument GTl. Query related information. Since GT1 has to retrieve the file data, you must first enter the self-diagnosis main menu. After the quick scan, click the "function selection" button, and then select and click on the "body" a "general electrical system" → "heating and air conditioning system" a "auxiliary fan", and finally click the "file" button, GTl will show support Fan circuit diagram, working principle, plug pin and component location map and other information. Look at the circuit diagram. You can see that the auxiliary fan has three operating gears. It is achieved by applying the battery voltage to the three ends of the two series gears. The specific line control mode is as follows:
  1 block: 1 gear relay to provide work power. Two series resistors are connected in series to the fan motor. 1 block relay for the four feet often open type, located in the engine compartment right rear electric control box. The relay terminal of the relay is controlled by the 18-pin and water temperature switch sensor of the air conditioning control module. The water temperature sensor is a 3-pin dual temperature switch type, located on the right side of the radiator. Its internal two temperature control switch, the closing temperature is set at 91. C and 104. C, when the water temperature reaches 91 ℃, 1 block relay pull, auxiliary fan began low speed operation.
    2 block: 2 gear relay to provide work power, a resistor circuit to the fan motor. 2-block relay is also a four-legged normally open type, located in the front passenger side glove box on the rear of the relay seat. The relay is controlled by the air conditioning pressure switch sensor, and the air conditioning pressure switch sensor is located on the drying tank. For 4-pin two sets of switches in the form of which 1, 4 pins are connected to the low voltage switch for engaging the air conditioning compressor with the electromagnetic clutch line: the sensor's 2, 3 pins are connected to the high voltage switch when the pressure exceeds 1750Pa. High-voltage switch is closed, 2-block relay coil is the high-voltage switch after the ride after the pull. The auxiliary fan starts running at medium speed.
    3 gears: the power supply provided by the 3 gear relay, directly to the fan motor. The relay in the form and installation location, and 1 block relay the same, the coil ends are controlled by the water temperature switch sensor alone. When the water temperature reaches 104 ℃. Relay pull, auxiliary fan began high-speed operation.
    It can be seen, this case is only the last one of the fault resistance line jumped open, 2 block and 3 block auxiliary fan cooling function still exists. When the vehicle is running, due to the high speed of the coupler fan and the wind speed of the heat dissipation, the symptoms of water temperature does not come out when the vehicle idle operation, due to low-speed operation of the coupler lantern. The overall system of thermal efficiency tends to be inadequate. The water temperature will gradually increase, exceeding the normal engine operating temperature. this problem. BMW E39 is also one of the common types of fault.