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      02-20-2014, 02:28 AM   #1
warranty
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More better interior light

On my E90 I recently changed all the stock interior incandescent lights to LED lights: 24-LED PnP dome light modules for the dome lights, plus typical LED maplight replacement bulbs. However, I was still unhappy with the relatively poor light output, so I modified the domelight assembly to maximize the light output while retaining the stock appearance and functionality.

What I did:
I modified the center domelight so that both maplights will also come on automatically whenever the domelight is on (such as when I unlock the car), while still retaining the ability to individually turn on the maplights when the domelight is off. Additionally, since I don't have a factory alarm I mounted additional LED lights (96 of them!) behind (inside) the grills of the domelight assembly in order to get more downcast light. NOTE: I have no idea if the E92 center domelight assembly is different from the E90's so somebody can chime in if they're indeed different. Here's what the end result looks like: both maplights are on automatically as the domelight comes on, with additional lights shining through the grills.


Parts/tools/skills needed:
- Exacto knife or a sharp utility knife to modify the printed circuit board
- (need 4) 1N5817 Schottky diodes: I got 10 of those for $0.99 shipped from that giant internet auction site
- (Optional) I bought 2 of those generic 48-LED panels (also on the auction site) and they just about fit behind the domelight grills perfectly

- Basic soldering techniques

How I did it:
First, a little bit of electrical geek talk here. Basically, I modified the domelight printed circuit board (PCB) and used "power OR-ing" circuits to feed either the original maplight power or the domelight power to light up the maplights. In other words, the maplights will be on if the domelight is on OR if somebody pressed the buttons to turn on the maplights. This power-ORing is done by cutting some existing copper traces and installing the Schottky diodes. The diodes I selected can each easily handle 12W of steady-state power (and up to 25A of surge current) so they should be fine with just about anything (including the stock incandescent bulbs) you throw into the light sockets. But enough greek (geek?) for now, on to the actual steps:

1. After removing the center domelight assembly from the car, the first step to modifying the PCB is to make two cuts to sever the existing power traces to the maplights. I used an exacto knife to do this, and you really only need to cut about 1~2mm into the PCB since the very thin copper traces sit on the very top surface of the PCB. I also used the exacto knife to scratch off some soldermask (the insulation layer of lacquer they put on top of the PCB) of one of the maplight power traces behind the cut so that I can solder on a diode later. You can see this illustrated in the following pictures:



2. Now it's time to install the diodes by soldering them on. The diodes are polarized (they only allow electricity to flow in one direction) and one end should always be clearly marked with a bar: electricity only flows TOWARD the bar. Basically, I soldered the ends of the diodes to the existing PCB connector pins and the solder pads that either already exist or I created. So, this is what the PCB looks like after all 4 diodes are soldered on (note where the bars are):


3. (Optional) The 48-LED light panels I got fit behind the grills of the center domelight assembly just about perfectly. Not all 48 LEDs will shine through the grill openings, but as you can see in the following pictures most of them will cast light directly down, and some of them are still visible at a slight angle. I just soldered the wires of those LED panels to the domelight power and ground traces of the PCB.



4. In case you were curious, most of the "generic" PnP T10 LED light bulbs don't work very well in the maplight sockets because the stock reflectors are designed around the incandescent bulbs. I found some generic circular 9-LED panels which fit behind the maplight lenses perfectly: I just used a dab of hot glut to secure them to the lenses. These are what these LED panels look like:


Summary:
It's really pretty easy. 2 cuts, 4 diodes costing about $0.40, and a little bit of time with a soldering iron. I'm pretty satisfied with the end result. The interior definitely lights up much better now--I want to see EVERY cookie crumb my preschoolers leave in my backseat dammit! One of these days I may remove and open up the front domelight assembly to see how to modify THAT, although on first look it may be a little more difficult to modify since there are no exposed PCB, not to mention BMW also crammed in the e-call/sunroof/passenger SRS lights on to whatever PCB sits in the front domelight assembly.
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      02-24-2014, 02:24 PM   #2
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very interesting writeup, while there is extra work involved i am sure this kit is beyond bright, any pictures installed? really curious on the 48-led panel
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      02-28-2014, 12:16 AM   #3
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LOL. i'm sure the output was worth all the trouble as this seems labor intensive. Pics for comparison?
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      03-01-2014, 04:08 AM   #4
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I didn't take before vs. after illumination pics: with my limited photography skills I couldn't manage any good "area illumination" pics either. Having said that, the increased illumination is definitely very noticeable since I use the child seats everyday. I'd say the rear seat area feels twice as bright now, which isn't a surprise since now I have additional 18 LEDs (from the map lights) and ~58 LEDs (visibly peeking from behind the "grill") in addition to the 24 LEDs in the PnP domelight module.
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      03-01-2014, 04:19 AM   #5
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If you're in norcal could I get one made too? I'll pay for the supplies! It'll be good for my daughter and detailing too. Have you tried the front window dome yet?
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