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Radar Detector Install - Audi A4

Prior Experience: Some electronics
Cost: approx. 5 bucks
Time: aprrox. 1 hour

Discuss this mod - Here

I am sure that this will work with all of the radar detectors which have cigarette lighter adapters. You will have to be careful, because if you connect something wrong, you could ruin your radar detector. So be careful, and read everything before you start.

This is a nice way to clean up the interior of your car. Most people just leave the radar detector low on the window and run that ugly ass cord down to the cigarette lighter. It looks stupid, and it is a pain in the ass to have that cord in your way all the time.

Audi A4 radar detector

SUPPLIES - Besides the radar detector itself, all you really need is a good 2 conductor wire. This can be anything you wish (obviously something that matches your interior. I went to the hardware store and bought a power cable for a lamp and used that. Some people prefer phone cord, etc. You can really use whatever you want because this is not a high-power unit.

What $$
Power Cable 2
Assorted spade connectors 2
Wire cutter/crimper ?

Ok the first thing you want to do is locate a switched 12V power source. There are a couple places to get this including the back of the fuse box, the ignition wires, etc. It is really up to you and you should just test around for one. For the B6A4's with a sunroof, there is a connection very close to the radar detector's ultimate location, that (I thought) would make things easier....more below.

Audi A4 radar detector  

Since we will be putting this under the rear view mirror, I tried to wire it into the power for the sunroof. There is a switched 12V power connection there. Here is how to get to it...

First you have to remove the plastic piece covering these two phillips head screws (it just pops out). After which you can unscrew these and lower the whole sunroof control panel from the headliner...

Audi A4 radar detector  

Pictured to the left is the backside of the sunroof control panel, and circled is where I made my first connection - the location of the switched 12V power.

When I tested this location, I used a standard light up voltage tester with the ground connected to the vehicles ignition. It was clearly switched with the key, so I figured all was good. In order to find a ground wire, I poked around the same area, and found one that seemed to work. When I connected to the 'ground' and the 12 switched power, the tester indicated power and therefore a good connection.


When I turned the car off, the tester went off, so it looked like a good selection - nice and close to the radar detector. I wired the whole thing up, turned the car on and I was getting erroneous alerts from the detector. Then after 5 minutes of driving it would turn off. This happened every time, and for about 5 minutes I thought I screwed up the radar detector. HOWEVER, as it turns out, that ground seemed to be a switched ground (or something crazy) that only stayed low for the first 5 minutes the car was on...after which it had a voltage which screwed everything up. Long story short, I had a great local switched 12V, but I needed to find a new ground...which was more of a PITA than you would think. So if you can find something else, go for it...if not, do what I did below


I have gotten really good at removing my A-Pillar coverings (from installing the TV's and boost gage) and I knew I had a ground I used once before. So I went ahead and did this.

First you remove your visor by unscrewing the two screws holding it in on the left.

  Audi A4 radar detector
Audi A4 radar detector  

After you get those 2 bolts off, you can remove the handle above the drivers window. To do this, you have to pull it down, and pop off 2 screw covers that cover 2 torx screws. I don't have pics of this because it took me 2 seconds to do. You will then take off the plastic insert that says "Airbag" and remove the screw found beneath it. From here you just pop the pillar off. You do not need to completely remove it, because we are only trying to run a wire down it (you may be able to run the wire without removing it at all, but it will be a pain in the ass)

You can now run the wire across the headliner, down the A-Pillar in into the fuse box area. You can see the bolt that I used for the ground below (It is also the ground for my boost gage light)

Audi A4 radar detector  

Like I said, there may be a better ground laying around, but I knew this was here, and was getting to sick of looking. I messed up once and I wanted to go with what I knew would work.

For the B6A4 owners, I think you can get access to both power and ground at the connector which gives the sunvisor mirror power/ground. I do not have this wired anymore since I installed the TV's...but you may want to check there.

So now with power and ground figured out, how do you connect them to the radar detector? Well if you have the typical cigarette style, it will just like mine. You can open up the cigarette connector end (usually have to unscrew the end of it, or unscrew a phillips head screw - depends on the model) and inside you will find this:

Audi A4 radar detector

Now I have played with these things at least a dozen times, and as you can see one wire goes to the clips on the outside, and one wire goes through the fuse, to the part that is usually spring loaded (straight through the connector). EVERYTIME, the wire that goes straight through the connector was positive, and the clips were negative. BUT, if you look at that pic....Red is not going straight through ....and we all know Red is supposed to be positive. I went against my previous experience, and decided to connect the switched 12V wire to the red wires, and the ground to the which wire. I AM LUCKY that I did not burn out my radar detector. This is NOT THE RIGHT WAY!

Audi A4 radar detector

This is the correct way to wire please look closely...
It is up to you whether you want to cut the connector off (making this permanent) or wire it all together somehow and hiding this big ass connector somewhere in your headliner. Since I was going all or nothing, I cut it off close to the radar detector and basically wired the entire thing with my own power cord....choice is yours

After you connect your switched 12V to the appropriate spot, and the ground to the correct wire, you can go ahead and hide everything and put your car back together.

I decide to get the suction cups off my window by zip tying my mounting bracket to the rear view mirror with black zip ties.

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