Why a Car Radio may Keep Blowing Fuses – What to Do

Feeling stuck? You’ve got an aftermarket radio, followed the wiring instructions including connecting the harness, and yet each time you turn the key to ACC mode or to ON, the radio fuse blows. What’s causing this? Where do you start?

This post walks you through what might be wrong and causing the radio fuse to blow, what tests you can do to find the fault and get the radio working again.

Reasons Why a radio Keeps Blowing Fuses

A radio may keep blowing fuses if there is:

#1. Wiring Fault

If the fuse starts blowing after installing and replacing a radio then it might be that there is a short in the wiring.

This can happen as you’re making the wiring connections for the replacement radio.

Inspect the wire connections you’ve just made and any other. Look for any exposed wires (along the wire lengths) that may be touching each other, connecting to the ground or the radio housing.

#2. Internal Fault in the Radio

There might be an internal fault in the radio which causes the fuse to blow immediately.

Quick Test

For this test, you’ll need an extra head unit. Swap the currently installed head unit with another then replace the fuse. Check if the fuse blows again with a different head unit.

If it doesn’t blow then it is likely that the fault is within the radio itself and likely rules out a wiring problem.

Alternatively, install the head unit (associated with the fuse blow) in another car that has the same make and model of radio.

Does it work well or blow the fuse too? If the fuse blows too then it’s probably a fault with the head unit. On the other hand, if the radio works well then it’s likely a fault in the wiring.

How you Can tell that a Radio Fuse has Blown

If the radio fuse is blown then the car head unit will not power on when the key is turned to the ACC or START/ON position and the radio power on button is pressed.

You may also hear a “pop” sound as the fuse under the hood blows.

To confirm whether a fuse has blown or not, inspect the fuse – remove it from the fuse holder and check if the fuse wire is intact or not.

Alternatively, use a multimeter set to read ohms to test the continuity of the radio fuse in the fuse box under the hood to check if it is blown or not.

Checks to Locate Fault Causing Fuse Blow

Testing the head unit

To narrow down the fault to the head unit or wiring, first, remove the head unit from the mounting.

Then replace the blown radio fuse with another of the same type and rating. Turn the key to the ACC or ON/START mode with the head unit removed.

Does the fuse blow or it remains intact? If the fuse remains intact, then probably it is a fault in the head unit. Otherwise, it is likely a fault in the wiring or wire harness.

Checking the wiring or harness

Inspect the wiring, with a special focus on the points where the wires are spliced or where there are bends or any object applying pressure to the wiring for

  • Damaged insulation and wires accidentally touching each other as you splice or connect to the ground
  • An internal short in the pin connectors connecting to the head unit

Related Posts

What does it mean if the fuse blows immediately after you turn on the key to the ACC or ON position?

If the fuse blows immediately then it’s probably a case of a short in the wiring or in the radio itself.

If the fuse pops after a few seconds then it might be an intermittent wire connection issue that shorts with excessive movement.

Closing Thoughts

If the radio fuse blows, it might be a wiring fault (especially in the case of a new radio install) or a fault in the radio itself.

You can narrow down the likely cause by removing the head unit and checking if the fuse still blows with the head unit removed. If it does then it’s probably a fault in the wiring.

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