The application of clamp meter in automobile diagnosis

After replacing the battery (this method can also be used to confirm whether other faults are causing abnormal starting before replacing the battery), if the normal start state is still not achieved, we can analyze the fault by examining the peak value of the starting current. The clamp ammeter should be clamped onto the thick positive terminal line of the battery (the general battery's positive terminal has two lines, one for the starting device and one for power supply). Set the clamp ammeter to DC current and enter peak measurement mode. Start the engine, read and compare the peak value displayed on the clamp meter with that specified by car manufacturers (as different motor models have different starting currents). 

If it is lower than normal, please check in this order: battery positive cable contact, starting switch SW, switch conduction spring, battery negative cable; pay special attention to potential poor contacts in these areas. First set your clamp ammeter function switch to DCA file. Clamp it onto a wire from alternator to battery while paying attention to aligning its arrow direction with that of current flow direction indicated on meter head. Start engine and observe LCD display showing charging current; after normal operation starts, this value will gradually decline which indicates normal functioning. To determine whether alternator is functioning properly: duty cycle refers to percentage of positive half cycle within a pulse signal during each complete cycle. In engine electronic control system testing, various electromagnetic valves operate using pulse currents such as electronic carburetor mixed ratio control solenoid valve, idle solenoid valve, EGR solenoid valve, activated carbon tank control valve and distributor hall sensor detection. By comparing measured duty cycle values with standard values provided by automobile manufacturers respectively for each component mentioned above，it becomes easy to determine their operational status.