How to Hardwire a Radar Detector in Your Car

how to hardwire a radar detector

If you are tired of the messy setup of your windshield-mounted radar detector, knowing how to hardwire a radar detector can make a big difference, not just visually but with performance as well.

As someone who’s been through years of putting up with a dangling power cord, I’d like to dive ocean-deep into the nitty-gritty of hardwiring a radar detector, and most importantly, showing you how to do it the RIGHT way.

Table of Contents

Why is it better to hardwire a radar detector?

When it comes to installing your radar detector, hardwiring offers several advantages over the conventional windshield mounting method. Here’s a breakdown of why opting for a hardwired setup is often the superior choice:

1. Clean Aesthetic: When you hardwire, you create a clean, aesthetic look that keeps your cabin clutter-free and professional in appearance.

2. Reduced Theft Risk and Use it More Places: Radar detectors left on the windshield are enticing targets for thieves, no matter where you live. By hardwiring and hiding your radar detector, it can lower your chances of having the device stolen. In addition, it can even help you use it where laws make it difficult.

3. Uninterrupted Visibility: Driving requires attention, especially nowadays. By mounting a radar detector on the windshield, especially somewhere in the middle, it creates an obstruction in your field of vision. In addition, your radar detector can become a potential distraction. 

4. Enhanced Reliability: Occasionally, bumpy roads can cause the power cord to unplug, and out of nowhere, 12V cigarette lighter outlets can blow fuses. This creates a reliability issue that hardwiring can fix, 100%. Overall, when you hardwire directly into the fuse box, you create a more stable power source.

Materials Needed for Hardwiring

detector hardwiring tools

Before we dive into the step-by-step guide on how to hardwire a radar detector, let’s talk about the essential materials and tools you’ll need to ensure a successful installation. It’s not rocket science, but having the right gear can make this process as smooth as silk.

Your Radar Detector – You’ll need to have a radar detector for this one, obviously. Don’t get confused and think you’ll need one of the ones you hardwire into your grill. Not at all, any windshield-mounted detector will do. I’d recommend you check out our guide on the top-performing detectors currently on the market.

Hardwire Power Cable – Depending on which radar detector you have, you’ll have to purchase the appropriate hardwiring power cable kit. For example, most current (as of 2023) radar detectors use the RJ11 plug to power up their radar detectors. In a few more cases, you’ll find some newer detectors made by Redenso, that use USB-C. On top of that, you’ll find some of the older, often lower-end detectors, use the barrel plug connector. 

Fuse Taps – A kit would usually come with a few different-sized fuse-taps. However, if you buy everything separately, look for one that looks like this.

Pry Tool Kit – Plastic pry tool kits are often sold for less than $15. Grab a good quality one that would allow you to pull back some of the plastic trim pieces of your vehicle, without damaging anything.

Multimeter – A decent multimeter would be good enough. With this tool, you’ll want to test volts and amps to determine the viability of the selected fuse slots. 

Wire Strippers – To ensure everything is clean cut, I recommend using wire strippers when you working with wires.  It’s a recommended tool to use across the board when working with electronics. 

Tape or Heat Shrink – Let’s not forget to tape off and heat-shrink all exposed wiring to mitigate the chances of a short and to reinforce the overall durability of the hardwiring.

Radar Detector Hardwiring Steps

Step 1-5 of wiring a radar detector

Step #1. Locate the Fuse Box: Most vehicles have a fuse box located in the driver’s footwell area, under the dashboard/steering wheel. I recommend you find the fuse box located under your vehicle steering wheel (or somewhere nearby). It can also be on the passenger side (use your vehicle’s manufacturer user manual to locate it).

Step #2. Identify Ignition-Controlled Fuses: Inside the fuse box, you’ll see a range of fuses and relays. You need to look for fuses that are labeled “IGN” (or IGNITION), “ACC” (or ACCESSORY), “12V” (12V SYSTEM), or anything else that powers ON and OFF with your key.

Step #3. Use a Test Light or Multimeter: To make sure the fuse you have selected is ignition-controlled, use a multimeter and set it to DC voltage. When the ignition is in the OFF position, probe the fuse terminal. If it reads ZERO “0” volts, the fuse is ignition-controlled.

NOTE: Keep the ignition in the OFF position.

Step #4. Connecting The Power Wire to the Fuse: Find the hardwiring cable of your radar detector by locating the positive hardwiring cable (usually red). Using a pair of wire strippers, remove a small section of insulation from the end of the wire.

Insert the fuse-tap cable into the empty slot where you just identified the ignition-controlled fuse.

NOTE: When inserting the fuse tap, ensure the tap is firmly secured.

Step #5. Connect the Positive Wire: Take the fuse tap and the exposed end of the positive wire from the hardwiring cable and make a solid connection by soldering or trying up the two ends together. Heatshrink the connection to ensure proper insulation.

Final steps to hardwiring

NOTE: Strip wires ONLY if the Fuse Tap and power wire of the hardwire cable do not already have male and female connectors included.

Step #6. Replace the Fuse: If there was a fuse in the slot where you inserted the fuse-tap, make sure to place the fuse back into the fuse-tap slot. In the hardwire kit for radar detectors, you’ll see two slots. The top slot will be for the fuse you pulled out initially. The lower slot which is in line with the wire, will require a new fuse for the new accessory (a 5A fuse will do), that you’ll be powering up.

Step #7. Finding and Testing Ground: Look for a suitable ground point near the fuse box or within your vehicle’s interior. Ideal grounding spots are metal bolts or screws that make direct contact with the chassis of the vehicle. 

To ensure you picked a good grounding point, touch one probe of the multimeter to the ground point and the other to a known ground, such as a metal bolt on the vehicle’s frame. If the multimeter beeps or shows continuity, you have a suitable ground.

On your hardwiring cable, find the negative (usually black) wire. Similar to the positive wire, (unless there’s an existing circular or half-circular connector) use wire strippers to remove a small to medium section of insulation from the end of the negative wire, exposing the bare copper wiring.

Step #8. Connect the Ground Wire: Once you are ready to make the connection, it would be wise to use sandpaper or something course to shave off any paint (if applicable) around the grounding point. This will increase the conductivity between the ground wire and the chassis of the vehicle.

Step #9. Testing the Connection: Reconnect the hardwire kit to your radar detector and make sure it’s securely attached.

After you have successfully completed the steps above, connect the other end of the hardwire cable to the radar detector. Turn the vehicle ON and OFF, both in the ACCESSORIES ON position and VEHICLE RUNNING position.

From here, you’ll be able to see whether the radar detector turns ON and OFF when needed.

Step #10. Feed Wiring Through The A-Pillar: Once you’ve confirmed that the radar detector operates as expected, disconnect the power cord from the radar detector. You’ll now proceed with hiding the wiring.

Take the wire and carefully route it up through the A-pillar of your vehicle. Use the plastic pry tool kit mentioned earlier to pull back or pop-off some trim pieces.

As the wiring makes its way up towards the headliner, be sure to carefully tuck the wiring between the roof and the headliner. Be gentle here to avoid damage, headliners often have clips/fasteners that keep them in place.

Step #11. Make the Final Connection: After you go through the plastic panels, behind the A-Pillar, and in between the headliner, you’ll be making your way to the radar detector. Make the connection with the radar detector from there and double-check everything to make sure this radar detector installation looks clean.

NOTE: Route wiring carefully in your vehicle to avoid obstructing airbags, which are crucial for safety. Know airbag locations, use existing wiring paths, and secure wiring properly.

Getting radar detector installed via hardwire

In Conclusion... It's Worth it

So now you have a pretty good idea of how much effort it takes to install a radar detector in your car, truck, or any other automobile. Almost anyone can do it, and if you spend any reasonable amount of time in your vehicle, you’ll see how using a radar detector is far more worth it.