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The mileage is about 160 thousand km, carrying the 5 shift manual transmission of the Citroen Fukang 1.6 passenger car in 2006. User reflection: the wiper is not working after the car. Inspection and analysis: maintenance personnel commissioning, confirm that the fault is present. After a preliminary understanding of the working principle and circuit diagram of the car wiper system, a series of inspections were initiated. The ignition switch is turned on, and the output voltage of the connector 2G1 is measured with the voltage meter of the multimeter. The measurement result is the battery voltage, which meets the requirements. Next, the output voltage value of the 2N2 pin of the connector is measured, and the measurement result is also normal for the battery voltage and the wiper circuit. Next, check the status of fuse F4 on the fuse box (Electrical Code 52). The fuse was removed and visual inspection revealed no fuses. The resistance between the 2 pins is also measured, and the result is no problem. Continue to measure the output voltage of the 4J3 foot of the connector (the ignition switch opens and closes 2 states). The result is that the output voltage is the battery voltage when the ignition switch is opened. This indicates that there is no problem for the wiper motor to provide power lines and fuse and circuitry to it. The output voltage of the 3M1 pin on the PB wiring harness (meter Ban Xianshu) is measured, and the result is the battery voltage. The output voltage of the 3M3 pin on the RD (rear wiper) is measured, and the result is also the battery voltage. The output voltage of the 2R2 pin of the connector is continued to be measured, and the measurement result is normal. The above measurement results show that there is no problem that the power supply line of the motor starts from the positive pole of the battery to the 9N8 foot of the wiper motor. Check the rear wiper motor and its line. First measure the state of the wiper motor's tie pin (connector 9N4 foot). The voltage is measured by multimeter and the measured result is 0 V. The resistance value between the tie foot and other normal foot of the car is also measured, and the measured results are less than 1 ohms. The above measurements show that there is no connection between the wiping motor's grounding and the fault. Check the state of the wiper motor after inspection. The post wiper motor is removed and the resistance values between the 9N4 foot and the 9N2 foot, the 9N4 foot and the 9N5 foot are measured, and the measured results are compared with the values of the normal windings of the wiper motor. For the sake of safety, a new rear wiper motor assembly has been replaced. Then after the wiper operation, it is found that the fault phenomenon still exists. The above operation indicates that the failure is independent of the wiper motor assembly and its working circuit. Check the right combination switches and their lines after wiper control. First check the F9 status in the fuse box on the line. It is normal to remove the fuse and see if the appearance is fusing. Next, using multimeter to measure the resistance at both ends of the fuse is no problem. Continue to measure the state of the right combination switch power supply line. Using the multimeter to measure the output voltage of the 11GB3 pin of the connector (the state of the ignition switch is open), the measured result is the battery voltage, normal. The voltage value of the connector 4J2 is measured (the ignition switch is turned on), and the measurement result is also the battery voltage. After replacing a new right combination switch assembly, a post wiper operation is carried out, and the failure phenomenon still exists, indicating that the failure is independent of the right combination switch and its working line. Check the rear wiper relay and its working line. First remove the relay and measure its internal resistance with multimeter. The resistance values between 9N6 and 9N1, 9NG and 9N8 feet meet the requirements. Replace a new front wiper relay assembly, and then perform related operations, and the fault still exists. The connection of the power supply line of the relay is measured. The results show that the line of the PB wire beam 3M1-3M3-2R2-9N8 foot is normal and the line of the 3M3-3M1-2J1-9N6 foot of the PB wire beam is normal, while the line of the 3M2-3M2-2R2-9N1 foot of the PB wire beam has a circuit breaker (in normal case it should be through). So careful examination of the circuit revealed that there was internal circuit breakage at the foot of the connector 3M2, and the problem lies here. Troubleshooting: replace the above connector and seal it according to the requirement, then do the work after the wiper operation. After that, the wiper can work normally. Review: the reason for the non operation of the wiper after this car is due to the circuit breakers of the PB wire bundle 3M2-3M2-2J1-9N6 foot which provides the working circuit for the post wiper relay. In this case, when the relay 9N6 foot is placed in the back wiper working position in the right combination switch, no battery voltage reaches the wiper relay 9N6 foot after the battery voltage arrives, that is to say, after the relay is connected, it is impossible to have the power supply to the positive pole of the rear wiper motor, so the post wiper can not work. For circuit faults, the existing faults are relatively easy to solve. Under such circumstances, the maintenance personnel should be patient enough to verify their judgement through various tests and measurements. This intermediate circuit diagram is an indispensable tool. All measurements and experiments should be carried out around the circuit diagram. With the deepening of measurement, the problem becomes clearer. In this case, by replacing the test with the appropriate parts, the fault area can be further reduced. With the narrowing of the fault area, there is no hiding place for the trouble spots anymore.