How to test a Car Amplifier with a Multimeter

Post by 
Tom Schaffer
Last updated on 
February 17, 2021

While finding out how to test a car amplifier might sound like a difficult and sophisticated task, if you have the right tools, it is not as difficult a task as it sounds like. In fact, having the right tools can save a lot of time and hassle. Besides, it will save you the money that you would be paying to the mechanic. However, there are a few key things that you must take into consideration before you test a car amplifier with a multimeter.

You will have to find out where the amps are located and then you need to hook the multimeter in and run a test. While multimeters vary across each other in terms of features, they all have the same operating principle. Based on the test result, you will have to make a decision. You can either make a simple fix all by yourself, or you might need to call a mechanical. In this article, therefore, we will provide you with a do-it-yourself guide for testing a car amplifier with a multimeter.

Testing, Preparations, and Expectations

These days, automotive stereos use complex technology. Gone are the days when you had sweet, single speakers mounted to the dashboard of the car. Testing those kinds of speakers was a matter of seconds. However, if your six-speaker audio system fails somehow, you will need to have a lot of patience in testing the system. The whole task can be quite frustrating. But it is still doable and you can save a lot of money that you would otherwise be paying to your mechanic. 


Keep in mind that if the main unit works, the problem is likely to be associated with the external amps. At the same time, note that not all cars rely on amps. Go through the manual carefully. If your car actually does rely on amps, then testing the amp will tell you if it has been getting the requisite power. If it does not, it won’t let the speakers play music, and hence, the problem. 

Configuring the Multimeter

Configuring the multimeter is an important part of the testing process. While it might seem like a complicated process, it is not. The black probe must go into the common socket, which is sometimes labeled as COM. The red one goes into the amperage socket, labeled as A. Some multimeters have two sockets, with one being more sensitive, whereas the other having a high amperage. If you are not sure which one to try, use the socket which has the highest rating.  

Following this step, turn the central dial of the multimeter to set the amperage corresponding with the socket. These settings might look different, but they mean the same thing. You might find A and mA settings on both the amp and multimeter. You might also find just one A setting on the dial. Keep the manual handy and double-check, if you are confused. 

Testing the Amplifier

The first step in this process is locating the amp. It can be anywhere, depending on the model and make of your car. It might be in the book, under the dashboard, behind a seat, and so forth. Consult the manual to find out where exactly it is. After locating the amp, check the wiring diagram to find out which wires need testing, as well as the characteristics that they should have. 

If your amp comes with more than one plug, go through the wiring diagram again to find out the main plug. It is usually the one that is marked 12V+. It could be hot at all times or only when the engine is on. This is the point where you can identify the crux of the problem. If it is not hot and yet, the system does not work, you will have to trace all the wires and look for a problematic plug, or a break in the wiring. This can be an extremely time-consuming and frustrating task.

Things to remember 

It is recommended that you should turn the power off before connecting the meter. This is because when the power is on, the current will instantly go through the circuit. Since the probe lead is small and covers a small area, it might heat up and weld itself to the amp. 

Besides, attach alligator clip leads. Since the probe surface is small, the high current can lead to its damage. If you are using alligator clip leads, the current is then distributed over a wider surface. In this way, the risk of damage is reduced. However, the power should be off while you attach them. 

In the following section, we list down some of the issues that you might encounter with your amp and how to resolve them. 

1. The Amplifier Does not Turn on

If the amplifier does not turn on, check the fuse by the battery. You can simply check this by looking at it. Sometimes, fuses are not blown but are simply bad. You might also be required to change a fuse. Besides, check the remote wire and the voltage at the amp terminal, if the amplifier does not turn on. 

2. Amp Goes on into Protect Mode

Your amp might, as well, go into the protect mode. In such a scenario, disconnect everything and turn the amp back on. Following this, reconnect your speakers. If your amp goes into the protect mode, it means the speakers have a problem. There might be a problem with the wiring, as well.

3. Amp Goes on Without Output

If your amp goes on without output, go through all the settings and check the volume levels. You might be required to make use of an alternative input for testing. 

4. Amp Goes on and off

If your amp keeps going on and off, run the system until the amp goes off and do a double-check of the voltage. If it goes under 10V, it means that there is a problem with the wiring, which you will have to fix. 


Thus, in this article, we provided you with an extensive DIY guide to test your car amp with a multimeter. While it is a task that involves a lot of patience, it is relatively a simple task if you do it all right. Besides, it can save the extra money that you would otherwise be paying to the mechanic. 


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