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Old 10-16-2012, 04:17 PM   #1 (permalink)
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Hello everyone! I have spent a few hours on separate occasions searching for answers on different forums and trying to find solutions, but to no avail. I can find bits and pieces of what I need to know, but nothing exact.

I was riding in my buddy's Porsche 911 Turbo a few months ago and was impressed with his illuminated door sills. So I got to thinking.......I can do that on my OBXT! I have all the materials purchased, and won't have a problem making the door sills. The only problem I have is the electrical part. I can solder, but I have no clue what to solder the lights to. I've got the puddle lights on my doors and may just tap into that source. But I've been reading other closely related threads about doing LED strips on the footwells, and some have come to the conclusion that tapping into the BIU would be the best source.

So here's my question: Does anyone have experience tapping into the BIU? I'm reluctant to just start screwing with it before I ask someone, because the part to replace it is quite pricey. If not, has anyone tapped into the puddle lights on the door? If so, do any of you have diagrams or have you seen threads with good directions on how to accomplish this? Any help/insight is greatly appreciated! Thanks!
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Old 10-16-2012, 07:25 PM   #2 (permalink)
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Cool idea, but wouldn't you have to re-program the BIU/computer to tell it to light up the door sills when the doors are open? That sounds so complicated. Tapping into the puddle light wiring seems much, much easier.
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Old 10-17-2012, 01:41 AM   #3 (permalink)
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That's the part I'm completely confused about. Sounds like a great idea, but the logistics of it aren't straightforward. I'm guessing what people have done is tap into a feed wire/line to the BIU the same way you would with the puddle light wires. Nonetheless, I'm still open to ideas. I simply want the lights to come on when I open the door.

I could also tap into the dome light, but that seems like a heck of a lot more work than I need to do to accomplish my goal...
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Old 10-17-2012, 09:53 PM   #4 (permalink)
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Bump 'n Grind....

Any insight anyone? Dig deep people!!! Maybe I can broaden the questions: "How can I make the lights on my project turn on when I open the door? Would you tap into the BIU or into the puddle lights on the door?"

Let me sweeten the pot: I'll buy you a six pack. (If you come to MT.)
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Old 10-18-2012, 08:33 AM   #5 (permalink)
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I don't get it, why don't you want to tap into the door puddle lights? Are you afraid that opening the door will be complicated? I can tell you that it is not difficult at all. It is quite easy, in fact.

Also, you may not even have to open the door. Just use a continuity meter to touch one probe to the bulb socket and then you can poke around with the other probe to see which wire corresponds to it under the dash right before the harness enters the door.

Then, you can tap the wire straight from under the dash, under the carpet, and to your door sill. What's the big deal?
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Old 10-18-2012, 07:12 PM   #6 (permalink)
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Not sure what you mean by "tapping into the BIU". I raise this because the door step light (puddle light) and the cabin interior dome light are controlled differently. This is apparent from the fact that, for example, when the door is opened, both come on, but when the door is closed, the step lamp goes out immediately, whereas the dome light fades out slowly. (Similarly, if a door is left open, the step light will remain on indefinitely, possibly running down the battery, whereas the dome light will eventually be turned off by the BIU, helping to prevent battery drain.)

The difference is that the dome light (along with others) is controlled by the BIU, whereas the step light is switched on and off solely by the door switch.

Both the step light and the dome light are connected to an always-on 12 V source. The low side of the step light goes to the door switch, which, when the door is opened, connects the low side to ground, closing the light's circuit and turning on the bulb. The low side of the dome light (when switched for "door" operation) goes to the BIU. The BIU provides the ground path to turn the light on and controls the current through it to slowly dim the light when the door is closed. The BIU is also connected to the door switch so that it "knows" when the door is opened and then closed based on whether the door switch is open (door closed) or closed (door open).

To get an added light to work, you would have to provide it with always-on 12 V power, and connect the other side to either the door switch line or to the BIU line that grounds the dome light, depending on how you want the added light to work.
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Old 10-18-2012, 07:21 PM   #7 (permalink)
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power from any of dozens of power sources under the dash or straight from the battery.

run the power through a relay to the lights you want to power.

then have the door switch signal trip the relay.
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Old 10-19-2012, 11:29 AM   #8 (permalink)
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Haha, I'm quickly finding out that I am deficient in my knowledge of electrical systems in vehicles (to put it nicely.) As I said before I can pretty much do anything else, but this electrical jargon is baffling. All I ask is to be patient.

And thank you all for taking time out of your day to help with my inexperience.

mike552, since I want the lights to only come on when the door is open, I my knee-jerk reaction was to assume that I should just tap into the existing light doors. I only brought up the BIU because I had seen it utilized in other threads. I have no doubt that it can be used (maybe by someone that has a tad bit more experience), but I am coming to the conclusion that might not be the best way to go. Even though I've never had the door panels off on this Subie, Ive had them off in all of my other cars, so I have no aversion to taking the doors off. But I like your straightforward idea of testing to see which wire is the door light and tapping in to that source under the dash. "The big deal" is the fact that I've just neveer done this stuff before, haha. Seriously, I'm a noob when it comes to electrical. Mechanical work I'm ok with. Electrical and body, get me a doctor, haha. Thanks for your reply.

plain OM, So what I'm hearing is that I can just tap into the dome source or door source? I want the light to stay on as long as the door is open, so the door (always-on 12-v) source is the winner, it sounds like. I am thinking people in other threads (adding footwell strip lighting to their Subies) were using one of the sources flowing into the BIU, such as the door or dome light wires. Your response was very informative, thanks!

grossgary, again - I'm new to this stuff, so I've never used a relay. From my limited knowledge, these are used as 1.) a switch, and 2.) a control over voltage, right? Or am I completely wrong on that? I'm looking for the easiest install and yours sounds like the more technical route. But if it is the right way to go, I will not skimp just because it is the harder way to go....I need to study up on relays a little bit, it sounds like. What I imagine is that when the door is opened, the door sill lights would come on. So using a relay would entail having a contact point on the door sill that is depressed to shut off the light, and pops out (when the door is open) to activate the light, correct?

Thank you all for your patience and responses. I ordered the parts yesterday, so I'm estimating they'll be here late next week. The project won't take up too much time, but I simply don't have a lot of time on my hands. I work 40+ hours a week and study about 30 - 40 hours a week. Needless to say, time is scarce. I estimate the project to be completed in 2 weeks, but as we all know, sh*t (oops, I mean LIFE) happens. I think I'll take photos of my progress throughout and post an update when it's all said and done with all the photos. I've had a few people say it's just a crappy idea, so I'd like to show them all wrong, haha.
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Old 10-19-2012, 12:20 PM   #9 (permalink)
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Quote:
Originally Posted by ChromeDomeAl View Post
mike552, since I want the lights to only come on when the door is open, I my knee-jerk reaction was to assume that I should just tap into the existing light doors. I only brought up the BIU because I had seen it utilized in other threads. I have no doubt that it can be used (maybe by someone that has a tad bit more experience), but I am coming to the conclusion that might not be the best way to go. Even though I've never had the door panels off on this Subie, Ive had them off in all of my other cars, so I have no aversion to taking the doors off. But I like your straightforward idea of testing to see which wire is the door light and tapping in to that source under the dash. "The big deal" is the fact that I've just neveer done this stuff before, haha. Seriously, I'm a noob when it comes to electrical. Mechanical work I'm ok with. Electrical and body, get me a doctor, haha. Thanks for your reply.

plain OM, So what I'm hearing is that I can just tap into the dome source or door source? I want the light to stay on as long as the door is open, so the door (always-on 12-v) source is the winner, it sounds like. I am thinking people in other threads (adding footwell strip lighting to their Subies) were using one of the sources flowing into the BIU, such as the door or dome light wires. Your response was very informative, thanks!

grossgary, again - I'm new to this stuff, so I've never used a relay. From my limited knowledge, these are used as 1.) a switch, and 2.) a control over voltage, right? Or am I completely wrong on that? I'm looking for the easiest install and yours sounds like the more technical route. But if it is the right way to go, I will not skimp just because it is the harder way to go....I need to study up on relays a little bit, it sounds like. What I imagine is that when the door is opened, the door sill lights would come on. So using a relay would entail having a contact point on the door sill that is depressed to shut off the light, and pops out (when the door is open) to activate the light, correct?

Thank you all for your patience and responses. I ordered the parts yesterday, so I'm estimating they'll be here late next week. The project won't take up too much time, but I simply don't have a lot of time on my hands. I work 40+ hours a week and study about 30 - 40 hours a week. Needless to say, time is scarce. I estimate the project to be completed in 2 weeks, but as we all know, sh*t (oops, I mean LIFE) happens. I think I'll take photos of my progress throughout and post an update when it's all said and done with all the photos. I've had a few people say it's just a crappy idea, so I'd like to show them all wrong, haha.
The easiest way to add a light is just as you describe - tapping into an existing light and adding in a new light. That will work fine for most things. Sill lights probably don't use up a whole lot of power at all (They are LEDs, I imagine?). You can drop those in there and have no issues at all. In fact, a relay is probably a waste when we're talking current draws that small.

For other installations (many lights or higher-current lights, like puddle lights, aux headlights, amplifiers, etc), you have to consider how much current is being drawn and what it will do. If a circuit is meant to operate a tiny door light and you add a huge mess of stuff to it, you could blow a fuse, or worse: burn out a wire, connector, or even the control module. Even if it does work at first, you'll have to wonder if today is the day where it stops working.

For those applications, relays are the way to go. A relay is a mechanical switch controlled by an electrical signal. You still tap into the door lights (or whatever trigger you want), but instead of pulling the power to run the lights off that line, you just use it to operate the switch. Minimal current needed, so minimal impact on the circuit. The switch itself can switch whatever you want! You can run a wire directly to the battery and switch that, powering 200W aux driving lights, or your amplifier, or whatever else you want (make sure to use wiring and fuses that are appropriate for the application).

A third option is actually the one I'd recommend, but I don't know if it's an option in the subaru without looking in the fusebox. If there is a fuse specifically for the door lights, you can go to an auto parts store and get what's called an "Add A Fuse" kit and use that (Google for Add-A-Fuse to see what I mean). What they do is replace an existing fuse in your fusebox with 2 fuses - one is the original fuse, the other is a new fuse that comes with a wire you can attach to. That should give you the benefit of a relay without having to actually wire one up. Again, I don't know if the door lights are actually on their own fuse or not.
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Old 10-19-2012, 12:47 PM   #10 (permalink)
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Can I back this up a bit for a moment . . ?

I've noticed that two terms are being used in regard to the desired lighting: "door sill" and "footwell". These, at least to me, are two different areas. I can understand lighting up the foot well area (the floor area of the front seats), but not the door sill (the part of the car body at the bottom of the door opening, more or less the top of the rocker panel). What is it that the Porshe has that's so desirable?

If it's lighting for the front seat area, have you tried the map lights? They light up a good part of that area, but in the 2007 don't come on with the dome light when the door is open. (That was added, I believe, in 2008.) However, there apparently is a mod for this. See this thread in the LegacyGT forum: http://legacygt.com/forums/showthrea...ght=dome+light (It's a long thread but worth reading through as follow-up posts provide additional ideas and experiences.)
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