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Add A Second Trunk Release Button to Foil Smash-n-Grab Thieves

Monday, March 23rd, 2009

I once had the displeasure of watching my coworker receive a phone call from his daughter telling him that her car had been broken into. She had been travelling with three friends in a large city for sightseeing and shopping. On the final morning they had checked out of their hotel room and gone to the local mall for a few hours before it was time to head home. Heeding her dad’s advice about keeping her valuables safe, she had the girls lock their cameras and laptops in the trunk with the luggage instead of leaving them in plain view in the cabin. The cabin was bare of anything remotely valuable when they left.

You can guess what happened. Someone apparently watched them move their bags to the trunk before going into the mall, smashed the driver’s side window, popped the trunk, and helped themselves to the contents. Three laptops, two DSLR cameras, a cell phone, and the luggage of all four girls was gone.

I sometimes store a computer or a firearm in the trunk of my car, so this bothered me greatly. Yes, part of the solution is not to be seen at your destination loading something into your trunk, but that’s not always practical.

I decided to add another button to my trunk release, so that both buttons must be pushed simultaneously in order to pop the trunk.

The concept is simple, and having heard it, you could probably figure out how to make it happen for yourself. Still, here’s pictures from my installation. The pictures are absolutely craptacular, as they were taken with my BlackBerry.

If you’re already into this sort of thing, this project will cost less than $5 and an hour of your time. You’ll need:

  • Two wires long enough to run from your trunk release button to your new button. I like to use pairs from cat5 cable for this sort of work. I picked the brown and brown/white pair. You may vary your color selection if you wish.
  • Button, button, who’s got the button? Any momentary pushbutton will do. I got a red one and a black one at Radio shack, $3 for the pair.
  • Scissors or a knife to strip wire.
  • Electrical tape and/or wire nuts.
  • Solder and soldering iron. Since this is in a car, a battery-operated soldering iron is preferred. You can use a traditional soldering iron with an extension cord, but make sure you’re using a heavy-gauge extension cord.

First, you’ll need to get to the wires behind your trunk release button. On my 1997 Mercury Sable, this is as simple as prying off the plastic cover around the button.


You’ll be picking one of the wires, cutting it, and attaching both ends to your long wire. You only need to cut ONE of these wires! ONE! I suggest waiting until you have the wire in place before cutting anything, as there might not be much extra slack in this wire to prevent it from falling back into the body.


I decided to mount my extra button with the sunroof controls, which are on the ceiling of the cabin above the rear-view mirror.


How you hide your wire depends on your car, but it’s not as hard as you might think. Most cars are packed with flexible trim that can be pulled back to hide a wire. People who install car stereo equipment do this all the time.


I was able to make my wire completely invisible to the user. Mission accomplished!


Cut ONE of the wires going to the button that came with your car. Strip a half-inch off both ends of this wire that you’ve exposed, strip your new wires, and connect each of your new wires to one end of the factory wire. Twist together and tape. You don’t *have* to solder, but I prefer to make a really good connection so they won’t want to vibrate apart later. Remember that your car gets very warm, and that will have an impact on your electrical tape. This means that you can use the tape to keep metal apart that you don’t want to touch, but don’t use it to keep things physically together if you can avoid it.


Even if you don’t solder anywhere else, you’ll need to solder now to connect your wire pair to your new button. This is how I mounted my button. I’ll note that if you get a small enough button, the diameter of it is small enough that you can skip the drill and just drive your hot soldering iron through the plastic to which you desire to mount it. I would never do such a reckless thing, of course.



Presto. If you press the red button, nothing happens. If you press the trunk release, nothing happens. If you press them both at once, the circuit is closed and the trunk pops open.

Alternately, you could completely remap your trunk release so that, in this case for example, the trunk release does nothing but the red button releases the trunk. I don’t recommend this for two reasons: First, anyone in your car who notices the strange button (kids?) will want to press it, opening your trunk. Second, many cars (like mine) will release the trunk even if you’re in gear and going 75 down the interstate. If If I’m trying to operate my sunroof, for example, I might accidentally press the button. As a second button, that wouldn’t do anything. As the only button, it will release the trunk lid. Bad juju.

Hope this has given you some good ideas. Obviously I can’t be held responsible if you monkey with the electrical system in your car and break it and/or yourself. Proceed with caution.

My Desk

Monday, March 9th, 2009

Flickr gallery here.

Again, thanks to xyankeeworkshop for the plans. I’m enjoying the setup immensely.