$6 LED Interior Light Conversion 12V DC Car/Boat/RV

This instructable might give you some ideas of how you can use inexpensive, off the shelf, LED lights to convert your car, boat or RV, interior lighting system. For about $5 US, you can buy a ready to use 12V LED light. I started with an amber side marker light, which included three bright amber LEDs in a ready to use device. My ten year old Suzuki/Chevy's interior light had been on the fritz for almost a year. Replacing the bulb didn't work; the time delay pwb (shown later) was bad, so I had a good excuse to do the LED conversion. The completed light is really nice. The amber light is easy on the eyes, and yet there's plenty of light to fill the car's cabin.

A few assorted observations...

Current draw of old incandescent bulb = 0.8 amps
Current draw of new LED conversion = 0.05 amps
LED Side Marker = Blazer International #CW1586A $4.97 USD*
*These lights sealed, which adds a few minutes to the job. If a suitable unsealed light is available, the unit will be easier to take apart.
Many people will have the odds and ends on hand to complete the job, but I threw in an extra dollar for solder, wire, etc...

Harvesting the Old/existing 12V Fixture...

Disconnect NEG battery terminal or pull the appropriate fuse and remove the lighting fixture from the vehicle.

Remove old bulb & holder, but take a look at the wiring and contacts; they may come in handy.

With my car, the dome light was a bit more complex than some. When the light was working, it had a time delay and fade-out which I actually found annoying. This added feature required a small circuit board, which had to be removed.

The sliding switch was still good and allowed the typical DOOR/ON/OFF choices.

Prepare LED Unit for Installation...

Remove unwanted hardware.

Remove lens - this may require a few minutes with a rotary tool if the unit is sealed.

Identify the Positive lead and the ground, or negative lead or contact.

Test the unit to make sure it works prior to installation.

If you're unfamiliar with how most automotive interior lights work, you may want to pay attention here... Most vehicles use negative or ground switching for interior lights. So when you open the door, that little button switch that turns on the light actually provides a path to ground, or the negative side of the battery. If your light has a sliding switch like mine, that switch is probably providing two possible paths to ground; through the door switch and directly to ground, thus providing light when the door is closed on demand. Slidinng the switch to the OFF position, simply blocks any path to ground or the negative side of the battery. (More about this in the next step)

Installing the LED Unit and Wiring It...

I used much of the existing wiring, metal contacts, and hardware for the new LED unit. For an explanation of how the sliding switch works, see picuture details.

I used hot glue to attach the LED unit and stabilize wiring, etc...

Install Converted LED Light and Test...

Actually, this was an easy job. It took longer to make this instructable than it did to do the project. This picture was take without flash, and although the three LEDs appear to be separate points of light, the actual light output is very even and more than adequate for the purpose of lighting the car's interior at night. The amber light is pleasant to the eyes too.