Failure phenomenon
A FAW Audi A4L 2.0T sedan produced in 2013, equipped with CDZ engine, automatic air conditioning, mileage 33 247km. The owner reported that after the ignition switch was turned off, the blower was still rotating. After temporary treatment in an auto repair factory, the blower could not operate.
Fault diagnosis and remove
1. Use diagnosis equipment to detect air conditioning control unit J255, store fault code: 01273, fresh air air blower V2, open circuit/short circuit to positive pole. Open the air blower switch and the blower will not rotate. According to the circuit diagram, check the plug of the blower control unit J126 and find that the air blower V2 plug is not connected, and the V2 plug is firmly inserted.
2. Test each speed of the blower, and find that when the air volume of 1 speed is large, it is small, and the rotation speed of air blower is uncertain. Turn off the ignition switch, then the blower will stop rotating, and then air blower will rotate at a higher speed, sometimes it will stop for a while, sometimes it will rotate all the time.
3. The Function of J126 is to supply power to air blower and adjust the rotating speed. Read J126 circuit diagram (Figure 64). T6y/4 is No. 30 electricity, and the measured voltage is 12.3V, which is normal. T6y/3 is ground wire, and the resistance between measurement and ground is 0.1 Ω, which is normal. T6y/1 The T20e/1 leading to the air conditioning control unit J255 is the control signal line, and the measurement conductivity is normal.
4. According to the measurement results, analyze the possible failure reasons: blower control unit J126 failure, air conditioning control unit J255 failure, basic settings are incorrect.
5. Make basic settings for the air conditioning system. The system display cannot be set. The storage fault code is 01087, and the basic settings are not made. Check the technical manual of the main engine factory and know that when the air conditioning system cannot be basically set, the software version of the air conditioning system should be upgraded from 0180 to 0181, which can be basically set after the upgrade. Turn on the air conditioner to run and query the J255 storage fault code: 01230. The left foot air outlet servo motor V261 is stuck or has no voltage.
6. According to the circuit diagram (figure 65), measure the V261 line normally, replace the V261, and the running air conditioner still stores the fault code: 01087, without basic setting. After basic settings, air blower works normally. No fault codes are detected and troubleshooting is performed.
Failure point: the software version has not been upgraded, and the left foot air outlet servo motor V261 is damaged.
Maintenance summary
Due to the fault of the left foot air outlet servo motor V261, the wrong air baffle position signal is fed back to J255, which leads to J255 wrong control of J126, thus causing the blower to be out of control.
