(WEN/Zhongxin Zhibao Xiao Pan Ren He Xin)
Failure phenomenon: A 2 0 0 9 Audi A6L, equipped with BDW engine, has a mileage of 135 566km, and the customer describes that the air conditioner is sometimes out of wind. It is true that the fault of the car test is received, and the air conditioner is adjusted to the maximum gear, and there is no wind.
Fault diagnosis and remove: we first connect the VAS5054 check 08 the fault code of the air conditioning system is shown in Figure 1.
According to the fault code analysis, the main faults are as follows: 1. Blower damage; 2. Blower resistor damage; 3. Air-conditioning panel problem; 4. Blower resistor line fault. According to the above ideas, first remove the blower, measure the resistance of 0.3 Ω, the resistance is normal, indicating that there is no problem with the blower, then measure the power supply of the blower, and find that there is no voltage of 12V, is there something wrong with blower resistor? Check the circuit diagram with questions: there are 4 lines to the controller, one of which is charger lead, one is ground wire, and one is signal line, there is another signal line with solar sunroof (this car can be ignored without this line). It is normal to use multimeter to measure charger lead and ground wire. The signal line has 12V voltage, which is no problem, so it must be the resistance problem. After communicating with customers, replace the resistance. After the replacement, the air conditioner is really windy, but the customer used the car for a day, and the fault was still the same. After arriving at the store, check and measure the line again. It is normal. Is there something wrong with the newly bought accessories? With doubt, I found a same and normal vehicle to adjust, and the result was still the same, which confirmed that there was no problem with the resistance. Is the signal voltage given by air-conditioning panel abnormal?
By comparison, it is found that the signal voltage of other vehicles has been beating at 10~11V, while this vehicle has been kept static at 12V, which obviously has problems. Is there a problem with the air conditioning control panel J255? However, after analyzing the circuit diagram, it is known that the C1 signal from J255 is also given to the pressure switch, and no fault is reported, which indicates that J255 has no problem and the possibility of circuit problems is extremely high, the on-off test of the signal line from J255 to resistor is abnormal. It seems that the problem has been found. On this line, check the two link plugs T14d/12 and T17h/14, no corrosion was found, but through step-by-step investigation, it was finally checked that one line under the brake vacuum pump had been broken, as shown in figure 2.
After re-welding, the fault is eliminated. Once again, the measured voltage keeps beating at 10~11v. Therefore, the voltage measured in the early stage is caused by virtual electricity. The main reason for later check is that the water accumulation is caused by Rhone blockage, in addition, this line has been squeezed and broken during the previous maintenance process, resulting in oxidation short circuit.
Maintenance summary: problems in the maintenance of circuits must be carefully considered and comprehensive, which are often caused by minor problems. In addition, when measuring voltage, you must leave your heart and mind guilty of electricity. This fault is confused by virtual electricity. In fact, the essence of the problem is not complicated.
