Car Amplifier

How to Test a Car Amplifier: Easiest Methods

caIf you think that your car amp is not up to the mark, there are several ways you can check by yourself. These include checking the car amplifier through a digital multimeter or voltmeter.

You can also go through a general inspection, but that can cost you a lot of time. As you’ve already guessed, we will give you a step-by-step guide on how to test a car amplifier through various methods.

What Is a Car Amplifier?

A car amplifier is a car’s sound system that amplifies input signals and converts them into sound through the speaker. The amplifier increases the strength of the input signal, and this amplifier output becomes an audio signal when hit with a speaker.

How to Test a Car Amplifier: General Inspection

Before diving into the technical methods of testing amplifier channels, it’s better to first try a general inspection. If you’re unsure how to do a general inspection, simply follow these steps:

Examine the Power

The power cable is the most vital component within an amplifier. If it doesn’t work, it’s hard for the amplifier to function correctly. To examine it properly, use these methods.

  • Take the amp’s power wire (the red one) and the ground wire (the black one) from the amp and touch them to the positive and negative terminal of the battery, respectively.
  • If you see the power light turned on, there are no issues with the amp’s power supplies.

Typical car amps consume power ranging from 12 to 20 volts, but 12-volt amps are most common. Check for fuses and circuits if your amp doesn’t turn on with the power.

Check the Wiring

Sometimes the amp current gets blocked with alterations in the wiring, resulting in a loss of functioning. You can check the car amplifier’s wiring diagrams to examine the circuit flow and ensure there isn’t an incoming signal blockade.

Diffuse the Fuse Problem

In many cases, there isn’t a problem in the circuit or input, and the core problem is the amplifier’s fuse. Damaged fuses can alter the continuity of the correct flow, resulting in weak or no input current in the power wire.

Usually, there is a central fuse placed in the amplifier’s chassis. If the amplifier power doesn’t turn on when its terminals are connected the right way, there are high chances that the fuse is the problem. The most common sight is corroded and cracked fuses.

Check the Amplifier Output

You can check if the amplifier is producing adequate output to subwoofers and woofers by following these basic steps:

  • Connect the RCA cables (the part of the head unit) to the speaker jacks.
  • Connect these speaker wires with the amplifiers.
  • If there is no difference in sound, then your amp and sound systems are working fine.
  • If there are audio disturbances or no audio signals from the speaker, then it’s time to thoroughly examine your amplifier.

Check the Car Amp with a Multimeter

A multimeter is an electronic device used to measure current, ranges, voltages, and other electrical measurements. To check the working of the amp’s incoming signals, you can attach a multimeter to it to measure it. Here’s how to do it.

Step 1: Locate the Amplifier

Amplifiers are mostly found under the dashboards or seats. If you’re unsure, refer to your car’s manual or find a wiring diagram to identify the amp’s location. You’ll find a 12V+ sign indicating the amp location.

Step 2: Power

Turn off the power of the car.

Step 3: Connect Your Multimeter

There are two probes for the multimeter. The black lead is for the common socket, abbreviated as COMP. The other one is used for amperage, abbreviated as A.A.

If you get two sockets in the meter, choose the one with the highest conductance ratings.

Step 4: VDC Setting

After connecting the multimeter, set your device to voltage direct current settings (VDC settings) to check the car amplifier. Please don’t select the AC voltage current, as it is majorly used for home theater amplifiers and large sound systems.

Step 5: Turn the Knob

The multimeter includes a voltage range knob that can measure the current until the required limit. Since most car amplifiers don’t exceed 20 volts, turn the knob to the 20V mark.

Step 6: Amplifier Testing

Turn on the power and ground wires after connecting the back cables and red cables (power and ground wires) with the multimeter. Your multimeter’s voltage value should be between 11 volts and 14.25 volts, indicating a normal amplifier working.

If there is no voltage or a drop in it, there are issues in the amplifier, especially in the circuit or fuse’s power supply.

Testing the Car Amp Through a Voltmeter

If you don’t have a multimeter, you can also use a voltmeter. This device tells you the amount of current going to your subwoofers.

  • Connect the amp’s speaker outputs to the voltmeter.
  • Set it to AC voltage reading.
  • Power the amp’s head volume.
  • The voltage reading will elevate.
  • Note the highest voltage reading.

To calculate your reading value:

  • Multiply the reading with the same value.
  • Divide that number with the subwoofer’s impedance.
  • You can find the subwoofer’s impedance written on the amp.
  • With these calculations, you’ll find the peak power of your amplifier.
  • If power is within range, then your amp is normal. If it’s not, there are problems in your amp settings or the amp itself.

How Do You Know if Your Car Amp Has a Problem?

Like other electrical items, a car amp gives certain signals before a complete breakdown. These may include not powering on, a disturbed bass sound or additional troubling noises, or no extra background noise cancellation. Here’s are a few signs to watch out for:

No Power

The main amp component that is easily disturbed is its power wire. Even when the ground and amperage wire are connected to the power source, it won’t power up. This can be caused by a number of reasons.

A loss in power can be caused by faulty wiring or fuse issues in the amp. Once you detect the problem through a detailed inspection, you can change the faulty wire or restore the power wire cable connection, resulting in normal amp functioning again.

Abnormal Sound Quality

Even when the amp is working, a change in sound quality is a vital diagnostic feature of a faulty amp system. The audio output may sound distorted, or there may be excessive bass in the audio. Along with that, the volume levels can seem altered.

Altered volume levels mean the sound can seem lower or excessively higher than its regular audio, which indicates a problem with these musical products. If your amp and speaker are working well, you will hear a fuller soundtrack with clean and distinct audio.

Distortion in sound quality could be caused by two reasons: either there is a problem in the map itself, or there are distortions in the sound systems or speaker wiring.

Activated Protection Mode

The amplifier protection mode is a condition in which an amp shuts itself down when there are threats of amplifier damage. When your car amplifier goes into its protection mode, it indicates that your amp is in trouble and may undergo irreversible damage soon.

Protection mode can become activated due to faulty wiring or damaged internal components that might need repair or replacement. It’s better to check the amp thoroughly to rule out other possibilities.


We all know that excessive heating can easily damage an electrical product. The same goes with car amps. When the temperature of your car increases continuously, it damages its internal components and connections. Extreme hotness causes damage to power wires.

Make sure that the amp’s cooling system is working properly and that there is adequate space around it to cool down.

Amplifier Restarts

If your amp restarts itself out of nowhere, there could be a connector or faulty power wiring issues. In this scenario, make sure to thoroughly examine your amp wiring and connections.

Amp Makes a Popping Sound

Whenever you hear a popping or snapping sound from the subwoofers, it is a distinct indication of a faulty amplifier. This happens when your amp doesn’t have enough power supply.

When you notice any of these features in your car amp, it may be time to test your car amp using the methods mentioned above and ensure it’s working properly.

Do I Need an Amplifier or Receiver?

A receiver is an amplifier with radio stations in it. A receiver can act as an amplifier and a radio station, but standard amplifiers cannot. It’s better to buy a receiver if you prefer a radio along the way.

Final Words

This article gave you a detailed step-by-step tutorial on how to test a car amplifier with a multimeter, a voltmeter, and general methods. We also talked about the major signs that indicate a faulty amp or its system. We are hopeful that you can easily fix your car amp or at least diagnose the problem with this guide.

If you enjoyed this article or are looking to start your car amplifier journey, check out our article on the five best car amplifiers for your bass.

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