故障现象一辆奔驰R350车(采用W251底盘),接通刮水器开关,刮水器无任何反应。故障诊断用故障检测仪进前控制单元(SAM),无任何故障记录。采用故障检测仪激活的方式对刮水器电动机进行激活测试,能听到刮水器电动机继电器吸合的声音,但刮水器电动机仍不动作。于是维修人员断定为刮水器电动机有故障,更换刮水器电动机后试验,故障依然存在。笔者接手该车后,首先检查前SAM(刮水器电动机的主控单元),未发现有故障记录,激活测试也确实能听到刮水器 Symptoms A Mercedes-Benz R350 car (using W251 chassis), connected wiper switch, wiper without any reaction. Fault diagnosis with fault detector into the front control unit (SAM), without any fault records. Activation of the fault detector activation of the wiper motor test can hear the wiper motor relay pull the sound, but the wiper motor is still not action. So maintenance personnel determine the wiper motor is faulty, replace the wiper motor test, the fault still exists. After the author took over the car, first check the front SAM (wiper motor master unit), did not find a fault record, the activation test can indeed hear the wiper