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How To Test A Car Amplifier With A Multimeter.

How to test a Car amplifier with a multimeter

First of all, it is essential to have a little knowledge about the amplifiers. Second, it is essential to be able to recognize the type of issue in order to enable oneself to find the solution. Whether you own a 4 channel amplifier or a 5 channel amplifier the basics are the same and focus areas are:

  • 1. Power
  • 2. Input
  • 3. Output


It has a 12v power wire that is from the battery.

The ground wire is connected with the chassis ground.

The remote turn-on wire that turns on the amplifier depending upon if the small wire has 12v on it or not.


If the amplifier isn’t turning on the remote wire after being 12v and ground but instead fuses, it is asking for an inspection.



The input signal is transmitted from low voltage RCA wires. It is because the amplifier needs a small amount of sound signal to clean it up with a headroom. So process and expand it with little distortion as a possibility.

Some amplifiers have the option of high-level input, but such amplifiers do not have a catchy sound. In addition, they may bring higher distortion.

One way to check an amplifier for the input working is to use one headphone jack to RCA inputs. The phone is to be plugged into the headphone jack, and music to be played while the amplifier is on. I am not able to hear audio that indicates that the problem exists.

To Start:

First of all, you have to locate the amp for testing to begin. Your amp can be mounted anywhere – under the dashboard, in the boot or behind one of the seats.

Manual can provide you with the precise location of the amp. You can find it to see the wiring diagram to see which wires are to be tested and the characteristics of the wire.

If your amplifier has been running on more than one plug, you will have to look at the diagram to identify the main plug carefully. It is labelled as 12V+. This wire is always hot or when the car is running. Turning on the ignition helps to figure it out.

If “12v+” is not hot and the system is dysfunctional, you will have to track down all the wires and find the problematic plug causing the breakage. This diagnosis takes a lot of time and can be exhausting.

Tips for amplifier troubleshooting:

If you find that everything is connected, but the amplifier is not working, the following tips and advice may help you sort out the problem.

1. Is the amp mounted to a non-conductive surface?

If the amplifier is making direct contact with the metals or even through the screws, a glitch is about to occur. This puts the amp in safety mode, and it may not be able to start sometimes. Make sure that your amplifier is not touching the conductive surface in vehicles.

2. Is the amplifier getting the right power and ground?

For the proper functioning of the amplifier, positive power input and negative power output is a must.

There will be no output if the wiring is incorrect or is not enough in size for the amp or if the connection is loose or a fuse. Check the fuse of the amp to make sure it isn’t blown and working fine.

Testing a fuse with multimeter:

Our eyes are not accurate enough sometimes, so after removing the fuse, check it with a multimeter. It should indicate zero ohms. Also, use a voltmeter to know the voltage between the amp terminals.

Tip: Using your car battery as a reference helps. The battery and amplifier both should indicate 12v.

3. Is the amplifier receiving an input signal:

The input signal in an amplifier is indicated by the sound coming from the speaker. Disconnecting the wiring of the speaker of the amplifier helps you to know about the movement. Use a speaker for testing; connect it to one channel at a time. If speakers work, there is undoubtedly a problem with the speaker wiring, functioning, or the connection is not too good.

If the testing speakers do not show any output after the amplifier is turned on, the problem lies in the amp since the input signal and power have been checked already.

With just basic know-how, testing a car amplifier using a multimeter becomes comparatively simple and helps you make the best of the stereo of your car.

Testing A Car Amplifier- How To Prepare - What To Expect:

With advancing technology, car stereos have become more complicated than in the past. Many of us have the memory of single speakers mounted on dashboards in the good old days. Then, it was a matter of seconds to test them.

Today, if you encounter a problem with your eight-speaker music system, you will require far more understanding of the problem, but you can still do it by yourself to save some bucks.

First thing first, see if the central unit is functional and lighting up. If yes, the cause of the problem might be found in the external amps. Keep in mind that not all cars work on amps. It depends on the model/manufacturing year of your vehicle.

Also please have a look at the car manual to check it. If you do not find a glitch in the amps, test the amplifier to see if it gets power. If not, it will prevent the sound from going through the speakers, which is the problem.

Configuration of Multi-Meter:

The process of configuration of the multimeter is straightforward, even for those who are fresh at it. Remember that the black probe goes into the standard socket, whereas the red goes into the socket labelled as A, which means amperage.

There are two sockets. One is the high amperage, and the other one is more sensitive. If still not clear about which should be given a try, go for the one having the highest rating.

For the configuration of the multimeter, turn the central dial to the amperage setting, which suits the socket. There is an A and mA setting on both multimeter and amplifier, but check the manual to see just one location on the dial.

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