Introduction: LED Trunk Light Upgrade
Imagine arriving at the airport a few minutes late. You have to park the car and grab your bags as quickly as possible. Your wife rushes ahead to start the check-in process. You pop the trunk and look around to get the luggage. Grabbing what you see, you rush into the terminal. It is only after you are halfway to your destination that you allow yourself the chance to relax and think. Suddenly you realize that you did not have enough bags and must have left one bag in the trunk. Due to poor trunk lighting and a dark parking garage, you were not able to see that you left one small bag sitting in the trunk.
Don’t let this happen to you. Upgrade your trunk lights using LED strips.
The pitiful light that most car trunks have makes it hard to find anything in the dark. Some car owners might be lucky to have two pitiful lights in their trunk, but I believe every car I have ever owned has only had one. And it certainly wasn’t overly bright.
Step 1: Getting Started
Since I had previously bought a white LED strip for another project, I decided to use it for upgrading the lights in my trunk. You can see from the before and after pictures how much of a difference is made with this light upgrade.
- Soldering iron
- Hot glue gun (I've been very pleased with this one, but any would work)
Note: The LED strips need to be 12V so that you can power them directly from the existing car wiring. Fortunately it seems like the easiest and cheapest LED strips are 12 volt. There are also various colors of white. I like the bright white, but you can choose any white you wish.
Step 2: Finding the Poles
The light in my trunk is a simple festoon-type bulb. These are very easy to work with for this project. These are the bulbs that look like little glass bottles (or barrels) with metal tips on the end.
If your trunk light is a plug-in type bulb it is a little more difficult, but not impossible. The next step will show you how I did mine and explain how you would do the ones with the plug-in bulbs.
But before you can plug them in you must figure out which of the two wires going to the light from the car is positive and which is negative. This can be done with a multimeter or you can actually just guess. With these particular LED strips and the way they are designed, it won’t damage the LEDs to plug them in backwards, they just won’t work.
It is not a good habit to just plug things in and see if they work. LEDs can be destroyed from too much voltage in the wrong direction. It just so happens that because you are using a known power source (12V car battery) and a known type of LED strips (12V), then the likelihood of blowing them out is slim.
To find your positive and negative you might be able to look on your old bulb and see if it indicates which of the two connectors are positive and/or negative. It is not likely you will find anything.
If you have a multimeter you can test the polarity very easily. If you don't know how, I found a good video that will show you. (But if you just hook it up and try, ignoring my warning to not do it, I won't tell anyone).
Step 3: Wiring
The wires that you connect from your LED strips to the existing light can be anything small enough to work with down to about 22 gauge (larger gauge numbers mean smaller wires). I just used some extra wire I had lying around. This isn't too critical.
The connectors into the existing bulb socket will be somewhat dependent on your existing trunk light. In essence, all you are really trying to do is get a reliable connection from your new wires/lights to the old trunk light.
The LED strip will have a small mark on it to show positive and negative wires (+ and -). You need to solder two wires onto those small copper pads. One wire will go to the positive terminal of the light and one to the negative. Because my wires were all white, I colored a small black line onto the wires coming from the negative side of the LED strips (you can see them in one of the pictures).
For my lights I could use either a male spade connector or female connector. If using the male connector you will slide the blade between the existing light and the metal clip that holds the light in place (and provides the electrical connection). In my case, I removed the existing light and used female connectors and just slipped them over the existing positive and negative clips.
If your trunk light is a plug-in type light you will need a way to get the wire from the LED into the existing plug. This can be done by soldering appropriately sized paperclips to the ends of the wires and plugging them into the plug. I would recommend a blob of hot glue between the paperclips so they don’t short to one another. Hot glue is an insulator (at least all the ones I have tested) and it is easy to peel away when needed.
Of course, if you don’t mind making a modification to your car’s wiring, you can cut the existing light plug off and connect directly to the original wires. This can be done by soldering a wire from the LED strip to the existing wire or making some type of quick-connect system. For me it was easier to plug into the existing light than to modify the wiring.
Step 4: Installation
After testing to see that your wiring is correct, it is time to install the LED strips. All the strips I have come with an adhesive backing. In this case, that is probably sufficient. Clean the area where the lights will be installed to make sure you don’t have any oily substance on the paint that will keep the strips from sticking.
I put a long strip across the width of the trunk closest to the opening. Then I put two smaller strips in the back of the trunk (towards the front of the car). The only reason for two strips instead of one longer one is that it seemed right and there was a natural break splitting a long flat metal peice into two halves. Not very scientific, but it worked.
If the adhesive is not enough to hold the strips in place, you can always use hot glue to hold the strips. Hot glue (or tape) will be needed to pin the LED wiring in place. Use hot glue wherever the strips are not sticking well. I also apply a liberal amount of hot glue to the end of the strip where the wiring is attached. I have found that wherever I solder wiring to the end of an LED strip the glue does not seem to hold well there. With some extra glue in that area you can take the stress off the adhesive for the rest of the strip.
It is time to plug in the wires and see if the trunk lights up like a lighthouse on a foggy night. Of course, if you are doing this outside in bright daylight you might not enjoy the awe of the moment.
Step 5: Enjoyment
If you have everything hooked up right, then the LED strips should work any time the trunk lights would have worked originally.
The airport scenario at the beginning of this instructable is not merely theoretical. When I showed my lighting project to a friend he told me the story of how he left one of his wife’s bags sitting in the dark trunk on the wrong end of their vacation. Oops.
Don't let this happen to you. Upgrade your trunk lighting with the modern look of LED strips.
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