How to Hardwire a Radar Detector

04th Jan,2022

While most radar detectors can simply be plugged in without any hardwiring, some people prefer to do the extra work for aesthetic purposes. If you don’t want a long cord hanging from your windshield and obstructing your view, you should consider hooking it up so that it has a permanent power plug to run off of. This process doesn’t take as long as you might think, and it will look a lot better than if you just plugged the device in and let the cable hang down.

The entire purpose of hardwiring a radar detector is to connect it to your vehicle’s fuse box. The power cable will go through the trim completely out of sight. By doing this you will make your vehicle less of a target for thieves, which is a nice bonus. It could also improve your chances of getting out of a ticket, as the police won’t be able to see the cable.

Some people choose to pay a professional to hardwire their radar detector, but it’s something you can do yourself in less than an hour. In this article, you will get specific step-by-step instructions that will clearly explain how to do this properly.

Required Materials for hardwiring a radar detector

Before you get started, you will need to have:

  • Hardwire cable
  • T-Tap
  • Add-a-Circuit kit

Hardwire Cable

picture of blue wires

The hardwire cable is essentially just the cable that will power your radar detector. It is also sometimes referred to as a direct wire cable. It goes directly from the radar detector to the power source, which in this case will be your car’s fuse box.

You will find that there are multiple types of hardwiring cables to choose from. The standard type is a basic power cable. Other cables allow for additional features like an alert LED and a button that mutes the device. You can even get hardwire cables that will allow you to use Bluetooth to connect with your smartphone.

In this article, we will only be dealing with the basic power cable, but you should spend some time reviewing your options. If you want a fancier setup, you will want to know what choices you have before making a final decision. If you’re still not sure it’s a good investment to get a radar detector, check here.

Add-a-Circuit Kit

image of add a circuit kit for hardwiring

To connect the radar detector to your fuse box, you will need to purchase what is known as an add-a-circuit kit. You can locate the fuse box in your vehicle by referring to the owner’s manual, as the location differs depending on the vehicle.

You will see that the fuse box is made up of multiple small fuses that each correspond to a specific component of your vehicle. There is a fuse for the airbags, stereo, air conditioning, etc. The add-a-circuit kit will let you install additional electronics to your fuse box. Make sure that you get a kit that will work with the specific make and model of your car. A simple Google search should provide you with the details you need to find the right kit. Most of these kits come with the standard cable as well as extra fuses for any other devices you might choose to add.

Plugging in the Add-a-Circuit

The first thing you will need to do is to plug in the add-a-circuit. You will have to locate the fuse that controls your vehicle’s ignition. There will be other components tied in with the ignition, so select one that goes off in your car. This way you will avoid draining your battery when it is not being driven.

Whenever you start your car up, the radar detector will automatically power up. Finding the right fuse will most likely take some time. You should check to see what component of your vehicle each fuse connects with so that you can select the right one. This information will be available in the owner’s manual as well.

Depending on the type of car you have, it might be necessary to manually turn your radar detector on and off each time. Some radar detectors with built-in GPS automatically turn off when they sense your vehicle hasn’t been moving for a while.

After you have located the proper fuse slot, you may remove the current fuse. There is a special tool that you can buy for removing fuses, but a regular pair of pliers should be adequate.

When you have removed the fuse completely, you will put it in the add-a-circuit. You will see the slots that the fuses go into. The bottom slot is where the original fuse goes, and the top slot is reserved for add-ons like your radar detector.

Make sure that you calculate the total amount of power that all of your devices use so you can select a slot that is slightly larger than the combined number.

Connecting the Hardwire Cable

Next, you will have to connect the hardwire cable to the add-a-circuit. The first method of doing this involves using the blue connector that is found at the end of the add-a-circuit. Strip the end of the cable if necessary before inserting it into the blue connector. Take a crimper and press down on the connector firmly but not too hard.

The other method of doing this will require you to use a T-tap to establish a solid connection with the wire itself. The T-tap will go through the cable’s insulation and make contact with the wiring. If the hardwire you have purchased doesn’t come with the required connector that goes into the T-tap, you can purchase it separately.

Connect the Ground Wire

The hardwire cable consists of the ground wire and the power wire. The power comes from the add-a-circuit, while the ground must be connected somewhere else. You can use ground wire from existing electronics or connect it to a metal part of your vehicle’s chassis.

The easiest way to connect the ground wire is to find some that are already near the fuse box. If you cannot find any, you will need to locate a part of your car’s chassis that is made of metal. Secure the wire to the chassis and you are good to go.

image of valentine one hardwired to the windshield mount

Running the Wires

Once you have successfully connected the hardwire cable to the add-a-circuit, you will simply need to run the wires and plug them in. The best way to run the wires is to start at the fuse box and work your way up. It may be necessary to take the body panels off to do this. Check to make certain that the wire isn’t in the way of the airbag.

If you have completed all of the above steps successfully, you should have what looks like a clean and organized setup for your radar detector. Remember to mount the device high so that it functions properly.

William Johnson

William Johnson is the owner and founder of He writes about car accessories, with his passion stemming from a deep enthusiasm for all things automotive. His website, RRD, focuses on in-depth reviews of car accessories to help people find the best and latest products in the market.