I wanted to hardwire my radar detector, but I wanted a mute button and alert led, something improved upon my last idea.
I decided to use one of the disabled buttons on the BMW F3x/F8x’s headlight module for the mute button. I create my own button contacts using copper tape to put over the top of the original module’s contacts. I also 3D printed an alert symbol that flashes in my HUD, but this is only noticeable at night, currently.
I’ve included links to the materials I used, but there are many cheaper alternatives if you shop around!
Hardwire kit modifications: (only if you’re doing a mute button or remote led)
Remove the existing led and mutton button from the circuit board. Use a small drill bit to drill new holes for each lead, and connect a wire and connector to each spot.
I also found that when using the red led hardwire kit, I had to add a resistor once I removed the signal led. The blue led hardwire kit already had this resistor oddly enough.
Remote notification symbol:
1) Print the housing. I used 0.3mm thickness and 20% infill.
2) Place the led of choice into the back plate, bend the leads appropriately to fit, and solder a thin wire onto the leads.
3) Cut a small piece of paper to fit inside the housing, covering the whole left by the alert symbol, This will help diffuse the light, as well as hold the symbol in place.
4) Using some glue (I used 3 dots of superglue) place the symbol on the paper, using tweezers to perfectly align the symbol with even borders all around.
5) Snap the cover onto the back plate and use some sticky back tape to affix to the hud. You’ll need to do some testing to position it right.
Mute button instructions:
1) Follow this guide to remove the tabs blocking the OEM button from depressing:
(Pro-tip, when removing the module, press down on the top of the clips from inside, until it’s about 3/4″ out. Then you should just barely be able to see the clip from the outside. Push down from the outside on the part of the clip you can see and it will come out nice and easy)
2) Next, we’ll make our own button contacts so the radar detector can tell you’ve pushed the button. Start by removing the black silicone/rubber. (Watch out for the clear grease over the radial contacts in the center of the board. Try not to touch it!):
3) Lay kapton tape over the existing contacts. I chose the top button, and to put a contact on both sides, but really one side should be fine.
4) Lay 2 strips of copper tape per contact, using the existing contact as a guide. You want the two strips really close so they’ll join when the button depresses, but not touching!
5) Solder your wire onto the copper strips. If you do both sides, make sure it’s wired so that either side closing would complete the circuit
6) Push the silicone back over our solder job. I found using some jumper wire worked well if I wiggled and rotated it while gently pushing inside each of the 4 nubs as seen below
1) Take down the panels from the driver and passenger sides by removing the 4 bolts on each side and gently tugging down.
2) Find the cigarette lighter plug on the passenger side and install the taps.
3) I used some heavy gauge wire to feed the power and ground wires from the drivers side to the passenger side through the spot the arrow is pointing at, with the cigarette lighter plug circled.
4) On the driver’s side, run the hardwire module up behind the headlight mode switch (that you modified if you did the mute button) like so (terrible drawing, I know):
5) Pop out the panel on the left of the dash, and pull down the rubber door seal from the frame.
6) Run the cable through the open panel and up to the spot where you mount your detector. Start with the plug where it should be and start tucking the cable into the trim as you go, working back down the a-pillar. To be even safer, you can run the cable behind the airbag by removing the trim pieces altogether.
7) Reinstall the rubber trim, panel on the left of the dash, connect your optional mute button and/or remote led, put the vent back in and you’re done!