How to solve the problem of excessive running noise of Computer fan?

Start the engine, press the AC button on the active air conditioning control panel, and operate the air conditioning compressor. If the air blown out of each outlet on the dashboard is cool enough, it indicates that the air conditioning compressor is operating normally. The electronic cooling fan in front of the condenser begins to operate, and as the speed of the electronic cooling fan increases, the noise will gradually increase, which can be clearly heard sitting in the driving room. Based on maintenance experience, it is known that after installing the new electronic cooling fan for testing, if the engine runs for 10 minutes, the new electronic cooling fan will still emit a "whine" noise, indicating that the fault has not been improved in any way. Connect the GTl tester for self diagnosis, select the 7-series E38 chassis model, double-click on the "IHKA Active Thermostatic Air Conditioning" item in the main menu of the electronic control system confirmation, and the GTl tester will quickly scan this item. After completion, click on the "Control Module Function" button, select the IHKA electronic control system, search for fault information, and store it once there are no problems.
To test the function of the new electronic cooling fan, the specific method is as follows: close the incineration switch, turn on the incineration switch, select the "Electronic Cooling Fan" test item from the "Component Control" function menu of the GTl310 tester, press the "Activate" button, and the new electronic cooling fan will gradually change from low-speed operation to high-speed operation. Stop after 30 seconds. By conducting repeated tests on it, the function of the new electronic cooling fan was determined, as there was no operating noise generated during the entire testing process. Exit the "Component Control" function menu, then restart the engine, select the "Diagnosis Response" function menu, and check the new electronic cooling fan operation data. Press the 'Display' button, and the GTl tester will display new electronic cooling fan operation data.