Failure phenomenon: a 2009 annual Yuet 1.8 automatic car, mileage 24000 km, equipped with a new set of alpha; series engine with CVVT technology, equipment, automatic air-conditioning system. When users complained that the car air conditioning, fan mode is selected when the foot blast also face the wind. However, the frequency of failure is very low, and no rules.
FIG 1
Check Analysis: vehicle control unit for air conditioning by the air conditioning system blower control (FIG. 1). Pressing the automatic (AUTO) button on the control panel air-conditioning, air-conditioning unit in accordance with the control signal from the engine coolant temperature sensor, an outside temperature sensor, interior temperature sensor and the illumination sensor to control the respective actuators, and automatically adjust the cooling capacity air supply system, the shortest time to reach the interior temperature set by the driver, then the minimum amount of air supply and air supply to maintain this optimal temperature. When pressed blowing mode selection (MODE) button, the air conditioning control unit according to the blowing fan mode and speed selected by the driver, and the vehicle is automatically maintained at a set temperature.
maintenance staff checked first fan mode function, found everything normal. Diagnostic testing with the result that no fault code conditioning control unit. Maintenance staff at that time that, more likely to fan mode motor failure, because the motor failure does not occur even if there is a fault code, which is consistent with the symptoms, and therefore decided to replace the motor. Because the fault does not appear that this is only based on speculation and made tentative replacement parts, so maintenance personnel to truthfully inform the user and ask the user to observe changes in the work of the air conditioning system. Users on the third day to shop reflect the fault persists and the fault does not change.
In order to find the exact cause of the malfunction, the fault must be reproduced. So maintenance staff repeatedly operating mode switch button, and finally a failure. At this time, the blower fan mode selected portion, but also the foot of the wind. I seize this opportunity, connection failure diagnostic, detection is still no air conditioning control unit fault memory. Check data into the data stream, reading out of the outlet 33 a percentage of the position sensor (FIG. 2). So when looking for a comparison test of the same model of vehicle, vehicle normally found in front of the blowing mode selected, theThe outlet position of the sensor data was 6.3 percentage, indicating the position of the breakdown vehicle flap duct is incorrect, it is likely to be a problem inside the duct system.
FIG. 2
Remove the air conditioning duct, check the inside of the evaporation tank air passage switching system, each flap found easily, without abnormal catching, it seems no problem. Considering the blower motor is a new mode, the possibility is still relatively large air channel switching system failure. Again carefully check the duct system conversion, repeated activities of all flap, observe the moving parts of the work, finally found flap shaft ventilation modes exist shaking (Figure 3), which is likely to be the cause. Accordance with the requirements of the mechanical system, with the gap when the shaft and the bearing tolerance, replacement must be matched.
Figure 3
Troubleshooting: Since the bearing and the evaporation tank flap is integral and can not be repaired, only replacement of the evaporation tank assembly . After replacing the test, air duct system is working properly. After a period of time up call, users have reported no problems occur again, bringing the fault completely ruled out.
reviewed: sporadic fault, the failure difficult to reproduce. In case of failure is not reproduced, maintenance and parts replacement carried out by the subjective judgment of people is often not correct, which is often the main reason for rework. In this case, after the first replacement parts, because the maintenance staff has experience in this area, so truthfully inform the user, so that users know that this is not a valid service, but their involvement in the diagnostic process failure, so when reproducing a fault, the user is not considered a repair, but with the active Depot maintenance. After the second pick, focused on the failure to reproduce, and when a failure occurs and master first-hand data for troubleshooting laid a good foundation. This type of failure is a mechanical failure occasional, instead of the usual type circuit occasional failures. It is a failure at a specific machine position, temperature, load and vibration conditions. As a result of mechanical and electrical integration, mechanical failure can now find the direction of the problem by the electronic control means of detection, this case is a good example. After the flap jammed, the motor will not continue to operate and generate heat it? Test proved is no. The control unit will remember it as a endpoint, each time the motor automaticallyStop here. Also in the examination analysis must pay great attention to detail, and found no problems if the flap shaft shaking in checking evaporation tank, and refitted lookout duct system, which will be completely disrupted ideas diagnosis, it is not sparing any details one of the basic quality of maintenance personnel should have.
(Kang Jian, Wang Jian)