Interior LED lighting
This is a very sparse description of what I did to add this feature. I recommend thinking through what you are doing very carefully before actually doing anything. I never drew anything up, but if I did it again I would. Take your time, and double check everything you do. I won't be held responsible for anyone attempting this on their own. You cut, drill, bend, or break pieces of your car at your own risk.
I am also assuming some basic knowledge of wiring and automotive modification. I don't describe every step in minute detail. If you don't know you have to strip the ends of a wire before soldering it to another wire, stop here and get someone to help you. If you don't know how to remove interior trim pieces, stop now and get someone to help you.
Ok, I stole this idea from Matthew C Smith at DTMPower.net, and he apparently stole this idea from BMW 540's and Audi A4's. I wouldn't know about that, but either way, I thought it was a great idea.
Basically, power is tapped from the lighted sunroof switch on the same circuit as the lights, so it only comes on with the rest of your dash lights, and can be dimmed. LED's are installed in the rearview mirror pointing downward at the center console. A lot more could be done with this, but not without being very RICE. I expect some people might compare this to the windshield washer lights, but oh well, I like it.
I got everything from Radio Shack and Home Depot. I already had a soldering iron and solder, but both are cheap from Radio Shack.
2 - 5mm, 300 mcd, 5 V, 30 mA blue LEDs
1 - pack of 1/4 watt, 330 ohm resistors
1 - pack of 5 LED snap-holders
1 - pack of assorted black heat shrink tubes
1 - mated pair of 2 prong connectors
About 2 feet of appliance wire (like lamp cord)
About a foot of regular stranded wire
18-20 gauge wire taps
I used 16 gauge appliance wire, this was TOO BIG! You can use anything, but a few inches of this will be exposed to view, so I wanted something that would look good. Black is almost mandatory, unless you have some kind of color scheme going on. I also used solid wire for some connections, this was difficult to work with. I would recommend like 18-20 gauge stranded copper wire.
The LEDs I used were one color and spec that I found. There were others. If you use anything different, you may need to use different resistors. I am not an electrician, so I can't help you figure out what to use. I called an electrician I know for help deciding on the right resistor. The more resistance, the dimmer the lights will be. I don't think a really bright LED would be very good. The 300 mcd is millicandle something relating to the light output. Your mileage may vary.
Drill with 1/4" bit
Again, please take the time to draw your plans and think carefully about what you are doing before taking any steps. And take your time when making any permanent modifications.
First, I figured out which wires to tap into. I checked my Bentley manual, and the brown wire was ground, grey/red was switched lighting. Your mileage may vary.
I cut about an 8" section of the appliance wire and installed one of connectors to the end of it. There were no instructions for this, I kind of figured it out as I went along. You could install a more permanent solution by just hardwiring, but I wanted the flexibility to remove the mirror easily, if necessary. Basically, there are 2 pairs of metal prongs, male and female, and a pair of plastic connectors, male and female. Crimp two of the like metal prongs to an end of the appliance wire, and insert the prongs into the plastic connector. Insert into the larger holes until it clicks into place.
Keep in mind that LEDs are polar, meaning there is a specific negative and positive. Always keep track of negative and positive whenever making any connections. My LED leads were slightly different lengths. The longer leg was positive.
Access the sunroof switch area by removing the plate that holds the switch. Also remove the dome light assembly, it makes everything much easier. Use the wire taps to connect the other end of the wire to the sunroof switch leads - negative to brown (ground), positive to grey/red. Again, your colors may be different. I drive a 1998 M3 4 door (E36).
Next, layout your electrical components. Here is what I had:
The black tubes are heat shrink tubing. Resistors are not polar, so they can go either way, I believe. They also seemed to work the same, whether they were on the negative or positive side of the LED, though I am not 100% on that. I connected them to the negative side.
Solder everything together, so you have two matching pairs of wire-resistor-led-wire. I tried to take a pic, but something happened to it, so sorry. If you are feeling lucky, continue. If not, check to make sure that when your lights are on, the LEDs come on. Again, if you don't know anything about electricity and things aren't working, get someone to help you. I am not motivated enough to write a 10 page dissertation on this project including every last detail. Heat shrink the exposed bits and pieces at the LED. Now, solder each of the pairs together so both positive leads are together, and both negative leads are together. Again, check to make sure everything works.
Remove your rearview mirror. Mine twisted at the base of the mount clockwise 45 degrees and came off at the window, leaving a flat metal piece glued to the window. Take the mirror apart. There is a seam that runs around the edge of the mirror housing. I used a screwdriver to pry the front away from the back, gradually working my way around the whole mirror. Put the front piece in a safe place. Decide on where your LEDs will be. I tried to go halfway between the center and the edge on both sides, and about the center of the mirror, front to back. If you have the LED mounts, you will need to drill two 1/4" holes to mount the LEDs. Drill another 1/4" hole in the back of the mirror housing for the power wire. BE CAREFUL DRILLING! Install the LED mounts from the outside all the way as far as they can go, so they are flush. Install the LEDs from the inside until the click into place. The fit will probably not be perfect, but it will be pretty good.
Use another piece of appliance wire, I used a foot, I recommend maybe 18". Attach the other part of the connector to one end. Insert the other end through the hole in the back of the mirror. Split the two leads about 4 or 5 inches. Tie one lead around the other in a simple overhand loop, so the wire can't be pulled out of the mirror. Slide more heat shrink onto the wire, then solder the appliance wire to the LED assembly, again, keep in mind negative and positive orientation. Your LEDs may be a bit loose at this point...try to bend and wiggle wires around so they are both pointed relatively downward. In my case, the LEDs are not bright enough that I can tell where they are pointing, but if they were brighter, it might be more noticeable. Reassemble the mirror.
Reattach the rearview mirror to the mirror mount, and run the wire under the headliner. Connect the two connectors together, put the car back together.
If you were careful, everything should work fine. Here is what the lights look like
Here is what the light looks like. This is a digital camera, so low light pictures are tough...the blue patch is a napkin I had in the car to show the light
The pictures don't do it justice. You can see the lights from the outside, so some might think this is very rice. I like blue lights, so I don't really care, and it adds a nice ambience to the interior. I plan to get more blue lighting on gauges and what not to continue with the blue theme.