Symptom: a Jetta GIX mileage of 150,000 km, the owner reflected in the car turning and braking will always be abnormal sound, the idle state of the body jitter powerful, air-conditioning without hot air without hot air.
    Failure analysis: the car after the idle instability, the degree of jitter in general, but not within the normal range. Air conditioning cold air normal, to be idle after a period of time, transferred to the hot air file, air conditioning without any response. Driving during the car, turning and braking are issued when the harsh noise. Idle instability in a variety of vehicles are common problems, and this mainly with the air flow meter has a great relationship, replace the air flow meter problem should be able to solve.
    Air conditioning problems are more complex, because the air conditioning system involves a large number of circuits, light from the outside can not see a specific problem, the need to remove the instrument table to check, but according to past experience, there may be some mechanical failure , Such as air conditioning cable damage, or air conditioning system, cold / hot transfer board can not work properly.
    Turn the abnormal response should be caused by damage to the outer cage, although it does not affect the normal turn, but if the time for a long time, resulting in steering axle exposed, and finally the axle damage, the consequences are serious. Most of the brake noise occurs in the brake disc there, the need for further inspection on the stage.
    Troubleshooting: After the shelves of the various parts, especially the situation of the wheel to check to ensure the safety of vehicles in the future.
    Then check the lower arm and found no loosening. Two front wheels outside the cage has been significantly damaged, mainly because the outer ball dust cover due to rubber aging rupture, resulting in its internal grease missing. Remove the dust cover check the axle, no excessive wear, you can also use. Replace the hemisphere cage and add a new grease to it.
    The wear of the brake disc was also evaluated when the outer cage was inspected. Although there is no need for replacement, but there are also security risks. To remind the owner to drive a period of time to the repair point to do check.
    Air conditioning inspection First of all, start from the circuit under the instrument table, in the inspection process, found this car must be in the roadside repair shop repair, because many parts have been replaced, which the technician to judge a great increase in the difficulties The Circuit check because of the very complex, here is not too much introduction, but the final discovery of the circuit is no problem, suspected or mechanical failure caused.
    The final breakdown of the crux of the fault in the hot and cold air transfer plate on the gear. Although this problem is small, but it can lead to air conditioning is not working properly, and it is easy to ignore this failure. After the replacement of the gear, air conditioning and returned to normal.
    Check the car, the above failures are excluded.
    Recommendation: General models in the idle state of the total jitter problem, in fact, the general gasoline car in the cold start when there will be this problem, its root is the cylinder of gasoline and air combustion is not sufficient, so the power to provide Will be insufficient, causing the car's jitter.
    Turn and brake when the noise must be more attention, this fault can not be ignored, especially for the safety of driving or not play a vital role.