Having a good ground connection is critical if you think about dynamic and sound quality coming from speakers and subwoofers.
Especially when you connect a strong amplifier, it is critical to have a solid ground connection point. But, how to find the best ground in the car just by using a multimeter? Let’s find out.
Generally, if you have a multimeter, finding a good ground point in the car is straightforward. First, turn on the multimeter and set it to OHM. Next, touch the probe to the battery’s negative terminal and the other probe to any metal point or connecting bolt you want to test. The good ground is when reading on the voltmeter is close to zero.
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Tip: The car metal chassis acts as a ground for the car audio system, but if you struggle to find a good ground point with the multimeter, you can run a ground wire directly from the battery to the amplifier.
From the wires I have been using, a Knukonceptz is the top one. I am happy, especially with their solid design and flexibility that is important in tight spots within the car chassis.
In the article below, I will go through the main concerns about measuring ground in the car and show you how to correctly find the best ground points using a multimeter.
How Do I Know if My Ground Wire in Car Is Grounded Properly?
The car chassis is connected to the car battery with many different wires. What can happen if one of these wires becomes loose?
The car audio system may not work correctly, or worse, there could be some damage done to the amplifier or speakers.
This is why it is essential to first check that your ground wire in the car has a good connection. The best way is to tighten all connection points in the battery and amplifier’s terminals and then check the resistance with a car multimeter again.
The car battery is the best choice for car ground connection in car system, but it may be necessary to use car chassis or car body, depending on how close they are to the car battery terminals and if you want to run the ground wire through the entire cabin.
If you measure the ground connection from the negative amplifier terminal and the battery negative terminal, and the OHM value on the multimeter shows zero or close to zero, your amplifier is grounded correctly.
If however, shown resistance is high and it goes over 2 ohms (in some cases can go to 20 ohms or higher), that means the ground is bad, and the amplifier will not receive enough current to function correctly.
In this case, you have to check the grounding point and make sure the wire touches the bare metal and sits tight.
If the wire connection is correct, and you still measure this connection with large resistance, you have to find another ground point and make the new connection to the amplifier.
What Should a Ground Wire Read on a Multimeter?
A car audio ground wire should be showing 0 resistance on the multimeter.
If you measure the ground connection between the car battery and any point in the car and the car audio grounds are bad, you will read low resistance between a few ohms to around 10 ohms.
It means there may be some tightening required or cleaning the connection to ensure the ground wire has direct contact only with bare metal.
In some cases, however, you can notice results of 30ohm or higher. This means your ground connection must be fixed by either changing the ground connection point or running the ground wire directly from the battery.
How to Check With a Multimeter if a Ground Connection in the Car Is Good?
A car audio system that runs from a car stereo and amplifier with the bad ground will not operate properly.
The best way to check and test different ground points within the car chassis is to use a multimeter. Multimeter needs to have an option to check the resistance (OHM), and this value will be different for different points you will measure.
For example, ground on the engine block can be very low, but the same measures at the rear seat belt connection can show a much higher value.
A few steps below will show you how to check the car’s ground connection using a multimeter.
- Before the test, make sure the car battery negative terminal is connected to the battery.
- Turn off all car accessories that can draw excessive current from the battery.
- Set multimeter to measure ohm (Ω) range and place one probe at the car battery negative terminal
- Take a second probe to a specific location in the car chassis where you want to measure a possible grounding point.
- Check different locations within the area close to the installed amplifier. Most of the measurements you will probably make in the trunk.
- Make a note of each measurement. The ground connection should be as strong as possible, especially for a strong amplifier, so you will have to choose later the area with the lowest measured resistance.
If you follow the above steps, you will find a good ground connection for your wire.
How to Test Ground Wire in Car With a Multimeter?
Testing the ground wire takes the same steps as all above, with the difference that you have to connect both probes to both ends of the same wire.
This measurement may seem pointless because of what could be wrong within the same solid wire, but there are sometimes internal issues caused by mechanical damage to the wire.
These cases can happen especially after a ground wire sits in tight bent places inside the chassis.
If you check both ends of the same wire and get high resistance results, the wire could be damaged, and you have to replace it.
Measuring the ground connection in the car with a multimeter is not difficult. Still, you must remember a few things like safety and not connecting both multimeter probes to both battery terminals.
If your grounding point is strong, you will see a low resistance close to zero ohms on the multimeter.
If not, you have to find another grounding point or run the ground wire directly from the battery to the amplifier.