How to use a multimeter to detect car leakage
1. Detection method
Battery power loss caused by the electrical switch not being turned off when parking; battery plate short circuit or oxidation shedding resulting in self-discharge and power loss; electric leakage due to electronic components such as automotive electrical appliances, wiring harnesses, sensors, controllers, actuators and circuit grounding Loss of electricity. Will make the car appear difficult to start or electrical failure phenomenon. There are many ways to detect whether the vehicle is leaking electricity, which can be roughly divided into the following types.
1) Current detection method
In the detection step, turn off the ignition switch, remove the negative terminal of the battery, adjust the multimeter to the ammeter (1A gear), and then take two wires, connect one end of the two wires to the multimeter's positive and negative test leads, and the other end to the negative terminal and Negative wiring, observe the ammeter value. Compare the measured current value with the maintenance data to see if it is within the normal range. If the measured current value is too large, it means that the vehicle has a leakage fault. Troubleshooting method Unplug the fuses one by one and check the value changes to -tg. When a fuse is pulled out, the current value becomes smaller, indicating that the leakage part is a circuit or electrical appliance passing through the fuse. After determining the fault range. You can check the circuit diagram or view the line direction. Find the damaged part along the line and repair it. If all the fuses are pulled and the ammeter value is still very large, it means that the fault point is on the line before the fuse, and you should focus on checking whether the line before the fuse has a short circuit to ground.
2) Resistance detection method
Detection steps Disconnect the ignition switch, and remove the negative terminal of the battery. Use an analog multimeter, and connect the black test lead to the positive electrode of the battery. The red watch pen is grounded. Adjust it to the ohm gear (Qxl gear) to measure the total resistance of the whole car: if the pointer of the watch does not move and the resistance value is very large, it means that it is normal and there is no leakage; ohm. It means that it is abnormal and there is a short circuit. Troubleshooting method Unplug the fuses one by one and observe the pointer changes. When a fuse is unplugged, the pointer no longer rotates, and the fault point is the circuit or electrical appliance passing through the fuse. With the current detection method ~ like. By consulting the circuit diagram or checking the direction of the line, find the damaged part along the line and repair it.
3) Experience testing method
The detection step is to disconnect the ignition switch, remove the battery negative terminal, and then touch the wiring to the battery negative pole to observe the spark intensity. The stronger the spark, the more serious the leakage phenomenon. Troubleshooting method If the spark is weak, it means that there is a small current, and you should focus on checking whether the small indoor lights, luggage compartment lights, etc. have the phenomenon of virtual connection and constant light; if the spark is strong, it means that there is a large current, and you should focus on checking whether Useful electrical appliances have been working or whether the line is damaged and grounded.
Let's take a look at how to use a multimeter to detect car leakage.
2. How to measure car leakage?
I often encounter customers who report that the car has no electricity after two or three days of parking, and the car cannot be started. Some can't even open the remote control door, and can only open the door with a mechanical key. When I went to the repair station for maintenance, they said that the battery was no problem. Because the car had leakage, it couldn't work. Many car owners didn't know what happened to the leakage. The following editor will talk about how to measure the leakage of the car?
Select the correct gear. There are gears for measuring voltage, resistance, and current on the multimeter. To measure the leakage of automobiles, the meter must be selected in the measuring current gear. Now the car is all DC, so it is finally on the DC current gear.
Select the range. When measuring the current, the gear range should be selected from large to small. If the range is too small, the multimeter will be burned out. Therefore, it is necessary to select the appropriate range from large to small. Generally, the range of the car is 10A. Now there are many meters that can Automatically adjust the range size, as long as the gear selection is correct.
Open the hood of the vehicle to be measured for electric leakage, turn off all electrical equipment on the vehicle, and then lock the door. If there is a remote-controlled vehicle, use the remote control to lock the vehicle.
Disconnect the negative pole of the battery, adjust the multimeter to the current gear, and adjust it to the minimum range.
Connect the negative lead of the battery to the red meter of the multimeter, and the negative pole to the black meter.
Wait for the various modules of the vehicle to go to sleep, and read the accurate static discharge amount. Generally, it is normal if it is within 50mA. The measured value in the above picture is 335mA, and the battery of this car is 65Ah. Calculate 65÷0.335=194.029851, 194÷24=8.08333333, that is to say, drain all the battery power in 8 days. The vehicle will not start in less than 4 days.
Next, you should check where to discharge. Based on past experience, it is easy to increase the static discharge by modifying electrical appliances in vehicles, such as adding navigation and audio. Many modified electrical appliances do not connect the power supply to the ACC gear, or the NO gear, causing the electrical appliances to continue to use electricity after closing the key to lock the door. After eliminating the modification, first look at the interior lights, door lights, vanity mirror lights, trunk lights, these are the places that are prone to failure. If there is no problem with these, start with the fuse box, and pull out the fuses one by one to observe the current change on the meter. For example, after the fuse is pulled out, the current on the meter drops to the normal range, that is, the electrical appliances powered by the fuse are discharged.
Many cars now use the CAN network. If a module on the CAN network has leakage, it will not work by dialing the fuse. Only by removing the entire module and measuring the leakage current to determine the quality of the module.
No matter what kind of vehicle is leaking electricity, our maintenance method is the same. We make judgments based on the method of first easy and then difficult. In addition, here is a maintenance point for everyone. Be sure to check the car before you start working. According to the actual maintenance experience, most of the leakage of the installed equipment is the cause of the installed equipment.
