The car electrical system shuts off while driving is annoying. Alright, I’m going to show you how to use a simple voltmeter to find electrical problems in your vehicle. Now realize that in your car, the battery supplies positive power and negative ground.
Often strange things happen to your car when you hit the brakes, and the parking light comes on. You could have nasty ground wire issues, which are frequently troublesome to find, and you can’t even see the electricity. So you need to test it using a voltmeter to quickly determine the cause of bad electrical problems in your vehicle.
Check Your Car’s Electrical Grounding With a Voltmeter
First of all, hook the meter to your battery, positive to (+) and negative to (-). Suppose the voltmeter reads a battery voltage of 12.85 V, which is a normal value for a good battery. Then what if you also want to check to see if the engine is properly grounded? Alright, that’s pretty easy.
It would be best to take the negative test lead from the battery and then clamp it on something solid like a metal part of the engine block. If you see it is still right at 12.85 V, the engine is completely grounded when it is turned off. But it’s not a good test because what you want is a real dynamic test. You want to see if it works when the car engine is running.
To do that, you have to test it again with a running engine. That way, you will know what voltage is when the alternator is running. Now suppose the voltmeter reads a value of 14.25 V. To ensure good grounding, you will disconnect the negative terminal lead again and connect it to the block.
After that, you will see the reading value on the voltmeter again. Suppose now the voltage is 14.27 V, the difference is quite small, only 0.02 V, meaning there is no problem with grounding. But if the difference in readings is 0.4 volts or more, then there is a problem with the grounding wire.
But, if it shows 13.05 V, you know it’s more than a 1V difference which means there’s a problem in your grounding wire. You may notice that there are grounded electrical wires everywhere on the car, like on the back of a firewall.
You can test it with the engine off and what engine on. from there, and you can see if something is not right. If you find that one of the readings is 0.4 V or more, there is a problem with the grounding of the wires. As such, you should trace the wires or connectors on the ends to see if they are rusty or loose. A bad ground wire will often try to draw power from another device and turn it on.
As a result, strange things can happen to your car. Suppose you stop hearing the brakes and the parking light will come on, it will start the device, or even the electrical system shuts off while driving. So when that happens, you most likely have a ground system that you need to check on your vehicle.
Now you know how to do a test with a voltage meter. It’s easy to tell if the ground isn’t working properly. So if you’re asking, why should you test it to a machine off and on? It’s because of the weak ground wire. It may work fine when the car is turned off. But while you’re driving, the power will flow to it. When it has a bad or short connection and ends up on it, it won’t need extra power. You will notice that a larger voltage drop means there is a problem.
So it would be much better to test the car’s electrical while they are working. Active dynamic tests are much better than static tests because what you want, everything works in the car while you drive it. You already know how to perform a grounding system voltage drop test. So remember, if you have a 0.4V overvoltage difference, then you have a problem with the grounding system. Hopefully, what you read can overcome the car electrical system shuts off while driving.
Ryan Daniel is a car enthusiast, and he has years of experience in the automotive field as an engineer. Now he is also active as an automobile blogger and member of the auto community.