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HomeTips & GuidesBlown Amp Fuse: 5 Reasons for the Blown Amp Fuses

Blown Amp Fuse: 5 Reasons for the Blown Amp Fuses

About Blown amp fuse, Whether on a long drive with your loved ones or driving alone, you need entertainment. The car’s audio system is your best entertainment companion. 

An audio system needs an amplifier to enhance the audio signals coming to the speakers. 

However, sometimes, the system stops working, and the most probable reason is a blown amp fuse. Read this guide to deeply understand the blown amp fuses and their diagnosis.

Table of Contents

Amp Fuse understanding:

Audio amplifiers in the car draw a lot of current, so you need to wire it correctly. Any faulty connection can lead to short circuits, overloaded wires, and accidental fires. 

The best is to use a separate power wire running from the battery to the amplifier in two ways with the help of an amp fuse. 

Firstly, it draws power through a single inline fuse that connects the battery and the amplifier, which has an internal fuse. 

In a second way, the amp connects to the distribution block (connected to the main fuse) for power. 

In some other cases, there are multiple amplifiers without any in-built fuses. It is advisable to use a fuse distribution block in this condition. 

As the inline fuse protects against faulty power wire, a fuse distribution block protects other amplifiers and their components when one amp fails.

Amp Fuse types:

Amplifiers that use internal fuses mainly use automotive fuses, which are standard fuses you may see in the other audio components of your car. 

When installing an inline fuse, you can use a blade fuse. In this case, the fuse is put in a fuse holder, which then connects to the amp power wire in line.

Another option for you is to use a barrel fuse. However, a clear plastic tube works as a fuse holder for these fuses. You can connect this holder in line with the power wire of the amplifier.

Picking a fuse holder with a rating equal to or higher than the installed fuse is essential. For example, if you want to install an inline fuse rated 30 amps, you cannot use a holder with only a 25 amps rating or less.

Amp fuse size:

The amp fuse size should be perfect for the smooth functioning of the audio system. If you use a too-small-size fuse, it will also blow out under standard conditions.

On the contrary, a high-rated fuse will not blow even in high-current situations. As a result, there is a risk to your audio components.

Further, using an inline fuse with a higher rating than an internal fuse is also essential. Doing this helps you avoid any risky situation. 

For example, if the internal fuse has a rating of 20 amps, the inline fuse should have a 25-30 amps rating. 

If you have two amplifiers with internal fuses, add the ratings together to calculate the rating of the inline fuse. 

Sometimes, amps do not have internal fuses. In such cases, the amplifier’s power rating lets you decide the correct fuse size.

What causes a blown amp fuse?

The wrong installation of any components can cause the wiring to heat up, blowing off the fuse. 

Check fuse and cable capacity:

Always see that the fuse’s rating equals the total current, which power and ground cables draw. 

Further, cable ratings should also meet the amperage requirement of the amplifier. Proper thickness cables shall not heat up on amp operation. 

Cables, fuse, and amplifier should match current ratings for the system to work smoothly.

Check for chafed cabling:

Improper installation of cabling may cause chaffing of cable insulation. If the conductor touches the car’s body part due to chaffed insulation, it may cause a ground fault. 

The ground fault will draw a massive current immediately, and the fuse will blow off. 

Always route cables from the firewalls with insulated openings so cable insulation is not damaged or cut.

 Never route cables under car carpets under the direct pressure of feet. The constant weight of our feet will damage the cables for some time. 

Always install cables through door jambs and keep them away from pinch points.

Reduce amp gain:

Excessive gain settings can cause the system to draw a high current. It can blow up the fuse. Do not confuse gain with volume. 

Use gain settings to reduce distortions in sound. Always first increase the volume to 75%.

 Then, slowly throttle the gain settings first up and then down to bring it to a level where distortion in sound completely disappears.

Check Ground connections:

Improper ground connections may blow up the amp fuse. Terminate ground cables properly using terminating rings and connect them with the bare metal part of the car. 

Use ground points given in the vehicle’s body by the manufacturer. If no such point exists, use the proper screw and washer to make perfect ground contact with the car’s metal.

 You can use star washers as they can pierce through the car’s paint and make effective ground contact with metal. 

Check internal defects in the amplifier:

If, even after proper grounding, correct ratings, proper cable routing, etc., the fuse blows, the reason is internal faults in the amplifier. 

Normally, in such cases, the fuse will blow up when you turn up the volume. However, this is also not always the case. 

Since many components are inside an amp, let professionals test speakers for faults.

Fuse distribution block

Fuse distribution block

Finding out the problem by diagnosing a blown amp fuse:

Technically, it is possible to identify a blown fuse by looking over it or through a test light. However, if you use an ohmmeter or voltmeter, you will get more precise results. 

While checking, you need to check the voltage on both sides of every fuse. 

Start checking from the battery or main fuse.

It works well if you find the same voltage on both fuse sides. However, it isn’t good if the battery voltage is at one end and not at the other. 

If the problem lies in the main fuse, you must consider timing. 

Insert a high-rated fuse in the head unit, keeping the battery and amplifier OFF. 

If the fuse blows away again when everything is in OFF condition, the problem is probably in the power line. 

This power line can be between the distribution block and the main fuse or between the main fuse and the amplifier (when there is no distribution block). 

Check the continuity between the ground and the amp fuse’s dead side to assure yourself of the power line issue.

 If everything is normal, an ohmmeter should read “overload.” 

On the contrary, if it shows continuity, you must check the entire power line to determine its connection to the ground. 

Sometimes, a power cable connects to the ground only when you drive on rough terrains or bumps, leading to a blown fuse. 

Diagnosis of a distribution block’s blown fuse:

Sometimes, there is power on both sides of the main fuse, but the distribution block fuse only has power on one side. 

Such a condition indicates the problem lies in the internal amp or the power wire. 

Depending on the amp installation and the routing of wires, you can identify the main culprit. 

First, check the power wire connecting the block to the amplifier. You may need to remove the carpets, panels, and other components to check the length. 

However, by doing this, you can find out the location of the power line where it is touching the ground. 

If doing this much looks tiresome, disconnect the power line from the amplifier.

 Keep the loose end away from the ground and see if the fuse still blows by replacing it with a new one.

 If the problem persists, the problem is undoubtedly in the power line.

 Get it replaced immediately. In the above condition, if the fuse does not blow, the problem lies in the internal amplifier. 

It may be challenging to diagnose and almost impossible to rectify yourself. Get help from professionals if you are new to electronics. 

Diagnosis of blown internal amp fuse:

Built-in fuses in the amplifiers are often serviceable by the users. 

However, identifying the reason for a blown internal amp fuse is far more complicated than identifying a shorted power wire. 

When the amp has power, but the built-in fuse has power only on one side, the amp has some internal fault. 

The timing of the blown fuse can give you an idea of the issue. A car amplifier gets power from two sources: the main battery and the other from the “remote turn on” volts from the head unit. 

Suppose the fuse blows when the head unit is in OFF condition, but the car’s ignition is in the RUN position. 

In this condition, no power comes from remote turn-on voltage, and thus, the real problem lies in the main power supply. 

Several reasons exist, like component failure over time, connecting too low impedance speakers to the amplifier, and many others. 

On the contrary, if the fuse blows when the head unit is in ON condition, the problem may lie in the amplifier’s output transistors. 

That may also happen due to component failure, transformer winding failure, or bad speaker wiring. 


You must purchase all essential wiring harnesses and cable assemblies when the improper power line causes the blown amp fuse. 

If so, contact us. We can provide you with the best custom cables for the smooth functioning of car amps and other automotive components. 

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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