1. Getting LEDs and supplies
You will need:
8...LEDs
2...12v voltage regulators (i prefer a the 1A, T220 case, its overkill but they are cheap and i have a ton of them)
4...270 Ohm resistors (1/8 watt minimum)
solder, an iron , shrink wrap +/- some wire.
Except for the LEDs you should be able to find most of this stuff at radioshack, but radioshack bins are always picked through and never get restocked. If you cant find the resistors and Voltage regulator locally, order from an electronics supply house like:
Digikey.com
12v regulator - Part#Link MC7812CT-BP
270 ohm resistor part #Link P270CACT-ND
or
Mouser .com
12v regulator - Part#Link 512-MC7812ECT
270 Ohm resistor - Part#Link 660-CFS1/4CT52R271J Bold
Italics
You will also need to order up some LEDs, you may have read this write up before and remember me recommending buying LEDs off ebay, well don't. Ebay sellers are to much of a crap shoot, some vendors sell crap low quality LEDs that will burn out, trust me this has been a hard learned lesson - stay away from LEDs on Ebay some are fine, many are junk and you cant tell which is which until you get them install them and the LEDs fail prematurely. Having bright angel eyes isn't that great when you have to crack open the housings a few times a year to replace burnt out LEDs.
Purchase from these sellers, i have bought LEDs from both of them and can attest to the quality of their merchandise.
BesthongKong.com
LSDiodes.com
its should be noted that both these sites sell high powered 5mm LEDs. Lsdiodes sells the THC3 LED that pulls 80ma and is very bright see this thread on HIDPlanet.com. Best hongKong sell a 100mA 5mm LED, Its brighter than the THC3, i have these in my halos now.
I mention this to let you know these are not the LEDs you want to use with the resistor values above. Also b/c they pull so much current there is heat issues with these that need to be dealt with if they are to last, I am not going to cover that here, this writeup is for a basic WHITE or BLUE 5 mm pulling 20mA, If you want to use other colors you will need diferent resistors.
2. Opening up the head lamps:
not as bad as it sounds set your oven to 200-220 degrees., take out the screws on the back of the lamp there is only 3-5, leave all bulbs, sockets and caps on there, otherwise you will get a lot of moister in there & under high heat and it will spot the chrome. Take the headlight wrap it in a wet towel, not dripping wet but a little more than just damp, once, around the headlight, the rest of towel goes underneath the head lamp and onto a cookie sheet, so the unit sits on 2 or more layers of wet towel. (That�s what�s its there for, to protect the bottom from the heater element -3 inches away from the cookie sheet. W/o it, the plastic on the sheet would melt, but the rest of the lamp would be fine.) Let it bake for around 20 min
While that�s cooking get yourself ready for when it�s done, have at least 3-4 flat head screwdrivers on hand and a razor knife. The sealant you are trying to heat up will harden back up to a point where it�s difficult to work with in 5-8 min at most once out of the oven. Take that bad boy out and start separating the clear from the black plastic. Start on of the medial edge (closest to the center of your car). Put a screw driver in pry a little, not to hard, a little at a time. Leave the screwdriver in place and start working away from where you started, making sure to unhook the tabs that hold the pieces together as you go, as it separates more and more: leave something in between so it does close back up, go as fast as can w/o deforming and nicking up the softer black plastic too much, but some is bound to happen. When you reach the point that you can see the sealant spreading apart like, bubble gum on the bottom of a shoe � on a hot day.
Take the razor knife and cut the goo, that should make separating the rest real easy. Once you have it in two pieces put the back piece aside and get to work separating the chrome from the clear plastic, there�s a few screws and sealant that will be getting hard by now, you don�t have to separate them completely just an inch at most. This is so you can slide the halos out of the large hole in the chrome where the parking lamp and signal would be (now attached to backing). Otherwise it�s real difficult to get them past a certain point where the clear and chromed plastic come close to each other and you will end up scratching the clear plastic. You will see what I am talking about if you don�t get those pulled apart a little bit.
3. Halos:
Remove the halos from the chromed plastic (2 screws a piece) and get them out of the housing. Now you got to get those old LEDs out, I was lucky some of mine had dislodged from the glue they sit in making my job that much easier, but not saying much about the quality of these. See if they can be GENTLY pried out w/ a small screw driver or knife but do this GENTLY! Where the LEDs sit in the plastic is extremely thin and "rough housing" these things will definatly lead to a cracked halo. If they don�t come out w/ a gentle prying get a pair of needle nose pliers and chip away at the LEDs, they crush up pretty easy, and just to say it again take your time be gentle, crush them up and clear away any pieces left stuck to the glue, I didn�t have much luck removing the glue its on there good and I didn�t want to fuck things up, so I just let it be.
Wiring for the LEDs how they are postioned
Then get your soldering iron and LEDs out. The circuit above is one that is designed for reliability, if done right & with good LEDs you will not have to back in the housings again....at least for the LEDs. The LEDS will be running at 20mA, though you may see in the specs sheets of the LEDs, that they can handle 25mA max, it is best to run them @ 20mA. I say this b/c heat kills LEDs. a LED running at 25mA is not much brighter than the same LED running at 20mA, the difference may not be noticable, but the LED running at 25ma does create more heat than the same running at 20mA.
with that said, 5mm LEDs don't put out much heat even when running at their limit, but in our application these LEDs will be directly in front of a projector pushing out a decent amount of heat. The projector will not fry the LEDs but if the LEDs are running at their max (25mA) and the projector is on, say on a hot summer day, then it is going to get hot in those housings. The LEDs will not be able to get rid of the heat they are producing, b/c there is so much heat already present in the housing and the LED will start to slowly burn itself up.
Just a little math FYI:
each LED will drop 3.4V (Vf or foward voltage), since we will be running 2 in series each halo will drop (3.4v x 2v) 6.8V (Vt or total Voltage). The circuit is supplied with 12V Vs or suppied voltage) so the resistor needs to drop the remaining(6.8v - 12v) 5.2V and will need to limit current through the circuit to 20mA (I or current in mA) we can get the value for the resistors (R resistance in OHMs) by using a modified version of OHMs law.
R =V/I
or
R=(Vt-Vs)/I
or, since Vt = Vf x N, where N is the number of LEDs in series (2 in our case)
R=((Vfx2)-Vs)/I
our values are as follow
Vs = 12
Vf =3.4
N = 2
I = 20mA or .02A
R = ?
So
((3.4x2)-12)/.02 = 270 Ohms
Just figured i would include that
we
Take 4 LEDs: trim the anode (+) on 2 and the cathode(-) on the other 2(see diagrams above), take the remaining long lead and bend it at a right angle as close to the base as possible, place them into the halo as the old ones were, w/ the internals of the LED parallel to the surface the halo is resting on, 1 anode and 1 cathode from each LED is in position to be soldered to each other and the anode from 1 and the cathode from the other standing straight up.
The glue remaining in the halo from the old LEDs will most likely prevent them from fitting well, don�t force them, take a small nail file or sand paper and file the led so it fits and the light will shine directly into core of the halo body, file the base and sides stay away from the tip, when each one fits the way you want place them both in there line up the leads that need to be soldered, don�t solder them while they are in the halo, rather when you get them in position, take a pair of needle nose and grab them by the leads sticking out, (making sure the LEDs retain the same orientation as they where in the halo), and solder them together. Put them back in trim the reaming leads sticking out leaving enough so a length of wire could be soldered to each, solder wires to them, then place a piece of shrink tube on as close to the base as of the led as possible (to prevent a short circuit). 
Then give them a test, w/ a multi test or batteries or whatever you have on hand,
Once you are sure they work and are satisfied with the way they sit, shrinkwrap both wires together, then put some clear glue into the halo and place them in there, and let dry. Put them into the headlight unit, solder and shrink wrap all conections and test it again, (test test, test, don�t wait until they are on the car b/c it really sucks to goes through the whole process to fix a small problem ).
3. Putting it all together:
Reassemble the light w/ the 2 leads exiting the unit press the unit together as best you can try and get the screws that hold it together in there catch , this wont always happen though. And test the halos one last time. If they work, back into the oven for 20, when you remove it have a pair of channel-locks or pliers on hand to squeeze the two portions of the light back to the way they were. And another test just to make sure every thing is Kosher. Put it back on the car wired the way you prefer ( to the parking light w/ fog light only,... look really good).
4. Enjoy!
-when I did this I did them on separate nights, try it - the difference is remarkable, those LEDS they came blow compared to the ones you put in
PAGE 3-How to make D2S bulb holder on MDX projector.
PAGE 4 -How to retrofit MDX projector into 2000-2004 Maxima projector headlights.
Page 5 -How to make clear lenses for turn/parking lights on 2000-2004 Maxima projector headlights.
Page 6 - MDX projector adjustmet (washer mod).
Page 7 - Pics of my car all fooked up.
