How to Test a Car Amplifier Using a Multimeter

You and your pals are planning a road trip, but your car lacks loud music. No need to worry. Simply acquire a quality amplifier for your car’s audio system.

However, you cannot settle for any amplifier without first testing it. Even if the brand is well-known, you shouldn’t completely trust it, regardless of how amazing the offer is.

Components of an amplifier

An amplifier consists of three components:

1. Power

It consists of the 12V power wire that originates from the battery, the ground wire that is connected to the chassis ground, and the remote turn-on wire that activates the amplifier based on whether or not the little wire has 12V.

Check the remote wire and fuses if your amplifier has the proper 12V and ground but will not switch on.

2. Input

Typically, your input signal originates from low-voltage RCA cables. This is due to the fact that your amplifier only needs a tiny quantity of sound signal to be able to clean, process, and expand it with minimal distortion.

In addition, certain amplifiers offer a high input setting. Typically, these amplifiers do not produce the most impressive audio. They typically contribute more distortion to your sound system.

To accomplish this, connect your phone to the amplifier’s headphone jack and play music while the amplifier is on. If you are unable to hear sound, your amplifier may have an internal flaw.

Checking your vehicle’s amplifier is a simple task. You only need a multimeter to test its functionality.

What exactly is a multimeter?

Owners are unaware of the electronic components of their car’s sound system.

If you are one of them, do not fear because we will explain everything to you. The purpose of a multimeter is to troubleshoot electric and electrical devices. In an electric or electronic circuit, the multimeter measures resistance, current, and voltage.

Technically, a multimeter is employed to determine the appropriate operating levels.

Two types of multimeters exist.

Digital multimeter

Analog multimeter

1. Digital multimeters

Digital multimeters are widely used because they are more user-friendly and display results in digits, hence lowering the likelihood of reading errors.

2. Analog multimeter

Analog multimeters have a needle that moves along a scale. They are inexpensive, but it is difficult for beginners to appropriately interpret the data, particularly on resistance scales.

Tekpower TP8260L Analog Multimeter With Black Light and Transistor Checking dock are the top analog multimeters on the market.

Each sort of multimeter has its own benefits and drawbacks. Therefore, it will be up to you to choose the one with whom you can collaborate.

How exactly does a multimeter operate?

A digital multimeter has two different kinds of leads.

The colors red and black Red is expected to be properly connected to the voltage, current, or resistance and is regarded as the positive (+) terminal.

In contrast, black should be linked to a ground or common port and regarded as a negative terminal (-).

The probes on the multimeter are used to grip the connections being examined.

Additionally, there are technical recommendations utilized to provide a connection point.

Typically, even if your amplifier’s connection is correct, it will not function.

Therefore, you must use a multimeter to thoroughly test your car’s amplifier.

In addition, it is strongly advised that you cut off the electricity before connecting the meter.

Checking your amplifier using a multimeter: 

Some may perceive the activity to be extremely tough, while others may not.

Nonetheless, we shall divide the task in half to make it more manageable.

  • The volt-ohm meter
  • The amplification device

1. It is a multimeter

You must first determine if you have a multimeter. It would be beneficial to purchase a high-quality multimeter.

After purchasing a multimeter, the second step is to configure it. This entails calibrating the meter based on the average amount of amperes flowing through the circuit.

On the circuits’ nameplates, the approximate maximum amperes are indicated, and on the multimeter, the maximum amperes that may be handled are displayed. Therefore, do not exceed the amperes indicated by the multimeter.

Consequently, configure the system using the following steps:

  • A multimeter includes both VDC (Voltage Direct Current) and VAC (Voltage Alternating Current) (Voltage Alternating Current).
  • The VAC combination is essential for testing items powered by a home’s electrical supply.
  • Comparatively, the VDC mode is essential while testing an automobile amplifier, thus you must set the amplifier to VDC mode, which operates directly.
  • After configuring the multimeter, the wires must be adjusted. As previously stated, there are two sorts of cables.
  • Noir and rouge
  • The black wire is often referred to as the ground wire and serves as the negative terminal, whilst the red wire carries current.
  • It is preferable to connect the black wire to the standard circuit and the red wire to the labeled A socket (amperage).
  • Rotating the central dial on your multimeter allows you to set the amperage.
  • Adjust the delivered amperage by rotating the central dial in conjunction with the socket.

Validating the amplifier

After properly configuring your multimeter, you can begin testing your car’s amplifier.

Following these procedures will allow you to test your car’s amplifier.

Determine the position of the amplifier in your vehicle.

If you are testing factory-installed amplifiers, which is the case in most situations, the position of the amplifiers may change depending on the automobile model or manufacturer. Therefore, the first step is to locate the amplifier’s mounting place.

Car amplifiers could be located below the seats, on the dashboard, or elsewhere.

The car’s manual will direct you to the precise location of the built-in amplifier.

Check the power fuse of the automobile amplifier.

Check the fuse voltage related to the amplifier to accomplish this.

Check the protective mode of the amplifier

A protective mode on an amplifier functions similarly to a shutdown condition.

Your amplifier enters protection mode to prevent further damage, despite the inconvenience.

An amplifier enters protection mode as a result of poor installation, improper wiring connections, or an internal problem.

Therefore, the amplifier must be tested by disconnecting all connections and turning it on. If the protection mode is active, an issue exists.

Connect a multimeter to an amplifier and examine the voltage coming from the cables linked to the car amplifier to test for wiring faults.

Validate the output

Plug the multimeter wire into the output channel to check the output frequency.

Check the reading on the multimeter. If it does not indicate any task, it means the output has failed. Your speaker has blown.

Check the signals of your amplifier

Attach the multimeter with the amplifier to check the amplifier’s signals.

If the amplifier signals are reducing, it means the amplifier will cause distortion.

Check the voltage coming from your amplifier

Attach the amplifier with the multimeter and check its voltage.

You must check the voltage source if the amplifier goes off.

There could be another scenario where your amplifier shows a voltage of fewer than 10 Volts. In such a case, you could damage your amplifier, and it is good to have a technician look at it.

Also, sometimes the amplifier you are currently using could have lousy ground, which could cause your problems.

How do you know your amplifier has terrible ground?

1. Overheating

Overheating an amplifier happens when the amplifier’s linkage is faulty or if the ground or wiring is too short. This occurs since the amplifier is not receiving enough voltage to give the desired output.

To offer uttermost grounding, ensure that your ground wire is almost the same accurate size as the power wire and is fixed firmly to a part of the frame that has been scoured free from any paint and sanded down.

The most common reasons for an amplifier overheating are:

  • Improper installation.
  • Poor construction quality.
  • Mismatch in impedance.
  • Insufficient power.
  • Improper ventilation.
  • Some amplifiers could be clogged.

The efficiency of an amplifier gives a hint on the quantity of power supplied to it, transformed to sound signals, and the amount lost as heat.

2. Clipped sound signal

Clipping begins in the form of resonance when an amplifier is required to deliver more power than it is capable of. It is a characteristic of poor grounding.

When you push an amplifier further from its capabilities to create enough power to replicate the input signals to the speakers( for example, due to a mismatch of impedance), it will be tough to magnify the input signal without reducing the quality of the initial signal. The signal will be amplified but in a badly distorted manner. This will affect the audio quality and put your amplifiers in danger of being destroyed by clipping.

Other factors that cause clipping are:

  • Low wire gauge.
  • Extremely high input sensitivity.
  • The need for a bigger alternator.
  • The source signal is over-equalized.

3. Unable to turn on

An amplifier that won’t turn on is another sign of bad ground. If the circuit that powers your amplifier is completed by grounding, an amplifier with the lousy ground will not turn on to begin with.

However, the ground cables and power must be very thick to satisfy the amplifier’s electrical current’s needs.

Otherwise, the amplifier will not turn on or not function properly.

Factors that lead to an amplifier’s failure to turn on are:

  • Absence of remote.
  • A blown a fuse.
  • Poor grounding.
  • Attaching an amplifier to a conducting material.
  • If the power cable has no voltage.

Therefore, select a suitable amplifier wiring kit to ensure your amplifier works smoothly. It is also crucial to check that your amplifier is grounded appropriately, with the ground cable fixed firmly and the connecting area cleaned free of any form of paint.

4. Restarting all the time

A poorly grounded amplifier will keep on switching off randomly.

Loose or incorrect grounding is amongst the most common causes of amplifier failure.

Therefore, make sure that every connection is firm, and no loose cable strands are sitting around that may cause a circuit breaker.

Also, verify that the ground connectivity is right, particular for tightness and security.

Factors that cause a continuous switching on and off of an amplifier are:

  • Poor connection of speakers.
  • Mismatch in impedance.
  • If the internal features have a defect.

5. Whining noise

Different causes might cause a disturbance that can affect the entire automobile sound system. This makes finding the fault very hard and time-consuming.

The two prevalent causes of these disturbances are poor amplifier installation and grounding.

To solve this, ensure that the amplifier is appropriately grounded and its metallic enclosure is insulated from the car’s frame. In addition, you can also use a noise filter or suppressor in some cases. Also, your ground cable should not be greater than eighteen inches long because a lengthier line can cause disturbances.

Furthermore, patch wires, ground cables, antenna wire, or other parts of your audio system can increase unwanted sounds.

The issue is finding out where the noise is originating from in the first place.

6. Burning or fire

The worst sign of poor grounding is fire or burning. This is because it exposes you and your car to danger.

Heat is generated where there is friction. In subject to which a faulty ground, either on the amplifier or where it is mounted to the frame of your car, could melt the amplifier ground connection, generating sparks and eventually fire. Therefore, constantly double-check that it is securely mounted to avoid tragedy.

How to Fix Your Car Amplifier?

If your amplifier was not operating appropriately or when you test it with a multimeter, you find any error you can fix as follows.

1. Gather the appropriate tools

The tools needed to fix your amplifier are:

  • RCA cable.
  • Cooling fan (not a must).

2. Remove the wiring

Next, remove all the cables from your car amplifier but remove the ground, remote, and power cable.

3. Check the connections of the amplifier

The amplifier is supposed to be connected to the ground wire.

The ground wire should be free of any rust and a metallic wire.

Also, check if the remote wire is hooked to the blue wire and connect.

4. Test the connections

Using a multimeter to measure voltage, test the connections.

##5. Inspect the amplifier

The connections showing no voltage of the amplifier may be loose or damaged. Therefore you must check the open hardware, screws, and nuts.

6. Reconnect the wires

It would be best if you reconnected the speaker wire and RCA cable. Ensure that the speaker connections are not touching the car else. It will create noise.

7. Check the transistor

Connect the transistor to the multimeter and check if any of them show zero resistance measured in ohms.

If anything is defective, then replace it instantly.

8. Turn down the gain

If your amplifier is heating, it might turn your gain too high.

If that is the situation, I would recommend getting an extra fan to cool down your amplifier whenever it gets hotter.

If you cannot fix the problems, then have a technician look.

Furthermore, it would be best to take some precautions when testing a car’s amplifier with a multimeter.


  • Never use a digital multimeter whose wires are damaged.
  • Always keep test leads and the dial in the proper position to make accurate measurements.
  • Never try to use the resistance when checking the power of your amplifier. It will damage your multimeter.
  • There are finger guards on the test probes. Therefore, for your safety, always put your fingers on the finger guards when testing the amplifier.


In conclusion, when you follow all the above steps correctly, testing an amplifier with a multimeter will be an easy task for you. Also, remember to take precautions for your safety and one of your devices.

Leave a Reply

Your email address will not be published.