Messing with the trunk light... - Mazda 6 Forums : Mazda 6 Forum / Mazda Atenza Forum
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post #1 of 7 (permalink) Old 09-16-2004, 09:59 PM Thread Starter
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I'm hoping someone can share some expertise with me on current/voltage, etc so I don't burn or short something out.

I've been wanting to tweak the car a bit in two ways with the trunk light. It only comes on when the trunk is open so I figured I would tap into it to (1) make my trunk light brighter and (2) make a trunk open indicator for myself.

So I got to the wiring back there. The two wires leading to the trunk light are pretty thin. You can see my not-so-know-how coming in here. I believe to strip the wire a bit I had to use the 22 gage slots on the wire strippers. I piggy backed some speaker wire (the only stuff I had on hand) that is about 16 gage on it. Now, I did this twice for the reasons above. I fed one set of lines down through into the trunk using those convenient holes right around the trunk light.

The other set I'm in the process of feeding through to the front of the car. On this line, I'm attaching a 194 bulb holder and plan to place a single led on it. Whenever the trunk pops open - voila, it lights up wherever I mount it on the dash. I'm currently looking for a trunk release button on a car (any car) that can be illuminated from the back. I'll mount this somewhere by the dash... I only realized tonight that our trunk release button is not illuminated (was going to buy a spare from Mazda to mod).

Plans for the other line were to connect either an LED strip of probably 3 bulbs or a similar 3-4 bulb dome light to mount near the original trunk light. That should be enough for me to actually SEE into the trunk at night.

So I'm all wired up and the lights work, but only as tested. I figured before I made it permanent I would find out if this is a bad idea. What concerns me is the original size of the trunk light wires and bulb. They are tiny. With this mod, I would not even use the original trunk light but I'll be powering 4-5 additional LEDs using a thicker wire.

Will I short anything - or worse burn out the original wiring by drawing too much current? I don't know all the numbers but from superbrightleds.com, the specs for a 3-LED light bar in white is 107 ma. Red is more at 250 ma. A single LED (inverted at least - I figure all will be the same) is 20-25 ma. Don't know the specs on the dome lights from autolumination.

I figure if worse comes to worse, I think I can at least use the one line with a single LED for a trunk light indicator up in my dash without a problem. Then again, my thicker speaker wire may still screw me.

Thanks in advance for your help. BTW... if anyone knows what kind of car has an illuminated trunk button, please let me know.

Please see pics attached for an idea of wire size (harder to tell though in the pics than in real life) and original trunk bulb.
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post #2 of 7 (permalink) Old 09-16-2004, 10:02 PM Thread Starter
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OK... trying again to attach pics...
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post #3 of 7 (permalink) Old 09-16-2004, 11:11 PM
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Quote:
Originally posted by first mazda@Sep 16 2004, 10:02 PM
OK... trying again to attach pics...
[snapback]304289[/snapback]
It looks like you've got the right approach...one more thing, though, is that LEDs have the advantage that they draw *very* little current compared to incandescent bulbs. The existing wires are more than thick enough to carry that current. What the LEDs will draw is insignificant compared to what the existing light already draws.

So use as many LEDs as you'd like and don't worry about the gauge of the wire. Remember that the polarity matters with LEDs, so don't install them backwards and burn them out.

Drew
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post #4 of 7 (permalink) Old 09-21-2004, 07:03 PM Thread Starter
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Hey, Drew...

Thanks for the advice. Can I ask, though... how many LEDs do you think it'd take to equal the draw and current of the current bulb in there. I have yet to permanently pull the bulb and take a look at it to see what specs are on it but it IS tiny. Just trying to figure out how many trunk light LEDs I can run max in it's place.

In the meantime, I got my trunk light indicator working! No more inadvertantly popping it and leaving it open...

I moved the TCS switch over one slot since I usually drive with my left hand and it blocks that center blank location more. I can't get in or out of the car without noticing this light on... still haven't seen it at night. Right now it's the hyper white cuz it's the only inverted bulb color I have. I will test out red and maybe even a high contrast color like green or amber when they come in.


btw... I know it may look a bit cheesy and I'll probably end up just removing the "trunk open" sign but it was just a test. Believe it or not, that silver matches the rest of the interior "aluminum" trim almost perfectly. This is only a temporary setup... as I'm still searching for a car that has an illuminated trunk button I can modify and get in there. I was just worried for now that if a family member borrowed the car and accidently opened the trunk they wouldn't be confused by the solitaire un-marked bulb that's shining.
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post #5 of 7 (permalink) Old 09-22-2004, 12:54 PM
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Quote:
Originally posted by first mazda@Sep 21 2004, 07:03 PM
Hey, Drew...

Thanks for the advice. Can I ask, though... how many LEDs do you think it'd take to equal the draw and current of the current bulb in there. I have yet to permanently pull the bulb and take a look at it to see what specs are on it but it IS tiny. Just trying to figure out how many trunk light LEDs I can run max in it's place.
Let's try to figure that out. A normal trunk bulb is 3W, and from a 12V power source, that means it draws 3/12 , or about 0.25 amperes. You mentioned the milliampere ratings for the LEDs you're using. 100 mA is equal to .1 amperes...so you can use 250 mA worth of LEDs. By the way, in LEDs, most of the power drawn is drawn by a resistor that designed to limit the current, and not by the LED itself.

The wires are sized larger than what's absolutely necessary as well, so you can probably draw much more current than the 3W trunk bulb without any risk. In fact, according to a page I just read, 22-gauge wire is good for over 2 amperes. Look here (go right to the paragraph that starts out "The total current capacity"):

http://www.berkeleypoint.com/learning/wire_size.html

Drew
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post #6 of 7 (permalink) Old 10-04-2004, 09:46 PM Thread Starter
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[attachmentid=477]
Thanks for your help, again, Drew. I'm glad you filled me in. When I was worried about running too many led's, I was only going to risk a few of them. After the information you gave, I picked up two sets of dome lights. I'm an idiot, though - as I didn't think about the fact that while they each had 4 led's, the whole dome was tiny compared to what I thought they'd be.

Here are the domes I picked up. The weather here just switched like a light bulb so tonight it was too cold to actually do anything of real quality. Instead, I just mocked a set up until whenever it was nice enought to do it right.

The domes come with 3M sticky tape on the back side but it's STRONG. So I just padded it with a couple of strips of regular 3M mounting pads. This also gave the little clearance in the back for the wires to sit ok when it was stuck on a surface. It'd be a lot brighter if the dome lens was clear but oh well. I've got a red trunk now that I can also see everything in.

I also messed my pants when I put all the wires down (when I realized I didn't disconnect the battery) and two of them touched. Car went *PFT* and died. It started but had a fit. Radio, doors, lights all went dead. Took a bit to figure out which fuse to replace but my God I'll never forget that again.
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post #7 of 7 (permalink) Old 10-10-2004, 08:09 PM
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Hi Guys,

Lets not play games with the hopeless rear trunk light.

In Australia, we are ditching the standard trunk light and installing 300mm CCFL's.

CCFL (Cold Cathode Fluroscent Lighting) ... a far more advanced form of neon.

Here is a link to see the end results for yourself:
http://www.sydneymazdaclub.com/forum...isplay.php?f=9

Warren
Sydney, Australia
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