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How to Bench Test a Car Radio

Bench testing a car radio is the essential step that must be taken before installing the car radio, especially if it is a used one.

If the radio is not turning on, this process will help determine whether there is some issue with the car radio or the vehicle wiring, fuses, grounding, etc. But, how should we bench test car radio? Let’s find out below.

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As a general rule, to bench test a car radio, you need a radio, a 12V battery, wires, and an antenna. First, connect the radio to the battery, and if the radio turns on, then your radio is working correctly. If not then there is some issue with the car radio.

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Tip: While testing your car radio, you may find that it does not turn on or function properly. By having it connected to the battery, you will not find out what could cause its malfunction.

To test car radio wiring, you may need the multimeter, allowing you to find out where the exact problem is or which wire (connecting point) you have to repair.

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In this article, I will dig deep into how to test a car radio on the bench. It will help you find out if any issues in the car audio system are caused by your radio or other car audio components. 

How Can I Test My Car Radio Without Installing It in the Car?

Testing a car radio before installing it is crucial, especially when you just bought a second-hand one.

This simple check can save you a lot of time, energy, and money. You can test the radio within a few minutes. 

To test a car radio before installing it, you need a car battery, connecting leads, and a car radio.

Follow these steps to connect the radio to the battery:

  • You will notice three wires coming out of the radio, yellow B+ wire, red ACC wire, and black ground wire. 
  • If you cannot find these wires, then make your own by cutting 2 feet long wires from a wire roll and connecting them at respective terminals of the radio. 
  • Connect the red ACC wire and yellow B+ wire of the radio with the car battery’s positive terminal. 
  • Connect the black wire of the radio with the negative of the car battery. 

If the radio turns on then, your radio is good. If the radio does not show light, then recheck the connections, and if it remains the same, there is some defect in the radio. 

How Can I Test My Car Radio at Home?

Testing a car radio at home is pretty easy, and by doing this, you can make sure that your stereo is working fine. To check car stereo at home, you need the following equipment:

  • An uninstalled car radio 
  • Multimeter
  • DC adapter of rating 12 V and 1A (You can use your desktop’s power supply or any other DC supply). 
  • Electrical tape. 

To test a car radio, you have to carefully remove it from the dashboard without disturbing any other wiring. 

  • First, cut the connector of the DC adapter with pliers, and you will see two wires coming out from the adapter. 

You can check the polarity of the wires by using a multimeter. Plug the adapter into a wall socket, and ensure that both cables are not touching each other to avoid short circuits before proceeding with the following steps:

Now use the multimeter to measure the DC voltage between these two wires.

When using a multimeter, it is important to note which wire has been touched by each lead. 

If the multimeter displays a negative reading, then the wire to which the multimeter’s red lead is negative. If however, the display shows a positive value, the wire touching the red lead of the multimeter is positive. 

Remember to unplug the adapter from the socket after this test. 

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  • Tie a knot on the negative wire of the DC adapter. 
  • Connect the yellow and red wire of the car radio with the positive wire of the adapter and the black wire of the car radio with the negative wire (on which you tied a knot) of the adapter. Tape the connections so that they don’t touch each other and also with the radio’s body. Now your car radio is connected to the DC adapter. 
  • Plug the adapter into the socket again and turn it on. If the radio turns on, it means that it receives power. Otherwise, there is something wrong with the car radio. 

The main step in testing a car radio at home is determining the positive and negative wires of the DC adapter. This setup also allows you to test your car speakers at home. 

Do All Car Stereos Have the Same Connectors?

All car stereos come with connectors that are used to connect speakers, power, and other components. 

Not all car radios use the same connectors. For example, some vehicles may come with a DIN connector similar to the standard harness, but pins may be connected differently. 

ISO 10487 harness adapters used today were designed in 1995, which set the standard manufacturing and wiring practices for head unit connections with the car’s electrical system.

The diagram below shows the configuration of the connectors according to ISO 10487 standard: 

Connector A is black and is always present in the car stereo. It includes the input power supply, ground, motor controllable antenna output, and other pins. 

The connector B is brown and connects all speakers – front, rear, left, and right. 

If you doubt that your car stereo connector’s configuration is different from standard, then buy a radio harness for a specific vehicle and match the colors with your existing radio harness. 

car radio harness

How Do You Test Car Radio Wires?

The primary purpose of the wires of a car radio is to connect the radio with other electronic components and provide sufficient voltage to the car stereo.

Therefore to make sure that wires are working right, you may need to test for both, resistance and voltage of the radio harness. 

Voltage Testing

To test the voltage, first, remove the connector at the back of the car stereo. Next, turn on the vehicle to “ACC” and use a multimeter to check the voltage.

Turn the multimeter knob to DC voltage, then touch the black lead on bare metal and red to the wire to be tested. You will notice that the multimeter is showing readings between 11-13 volts. 

Continuity Testing 

Check continuity of radio wires is simple. First, turn the multimeter to continuity (diode or wave symbol) and then touch the leads at the ends of the same wire.

If the multimeter beeps, then the wire is good, if it doesn’t beep, the wire is damaged, and you have to replace it. 

How Do I Find a Short in My Car Radio?

All the electrical components of a car derive their power from the battery. In between the car radio and battery, there is a fuse and a relay to protect your radio from voltage spikes. 

To check the radio for short, follow the steps below:

  • Turn off the car first, then open the fuse box and locate the radio fuse.
  • Disconnect the wire from the battery negative terminal. 
  • Turn the multimeter knob to mV and touch leads from the multimeter to both ends of the fuse.
  • If the reading is zero, your car radio works fine, and you do not have a shortcut. If the reading is greater than zero, there is a short circuit in the car’s electrical components.
  • To confirm if the radio is short or not, remove the radio fuse and see if the multimeter reading drops. If the reading stays above zero, then the car radio is short. 


Whether you are installing a new radio or aftermarket radio, it’s better to bench test it. The information provided above provides you with all the tactics you need to bench test your radio. Now roll your sleeves and get back to work.