Interior Lighting via Ignition Key Light

Ramon · Sep 17, 2007

I had previously posted here about the possibility of powering LED interior lights via the ignition key light so that they would automatically turn on and off with the rest of the car's interior lighting. I was interested in the key light in particular because it's a lot more accessible than the overhead map lights, which would normally be the most logical way to connect additional interior LED's. I finally got around to finishing my "experiment" and I'm pleased to report that it works! :thmsup: I now have an auxiliary 12V source under the dash that can be used for any type of lighting, and it responds automatically to things like opening/closing of any door, alarm arming/disarming, and turning the ignition on/off (basically everything the key light normally responds to). Here's a quick rundown, with photos below to hopefully further illustrate what I did:

Fuses: First thing I did was remove fuse #13 in the under-dash fusebox to cut power to the ignition key light. In addition, I also ended up removing fuse #13 in the engine compartment fusebox (just happened to be the same number); This is apparently for the horn, and I accidentally shorted it

while working in the steering column area.

Steering Column: The top half of the steering column cover just snaps off by pushing up on it, and the bottom half of the cover drops off after removing three screws from underneath. With the covers removed, I was able to disconnect the green ignition key light connector by depressing the release tab on its back-side.

Connector: Power for the ignition key light is provided by #5 (white/black, ground) and #6 (red, 12V positive), so these are the two wires that I tapped into. I just used 2-conductor speaker wire (20 or 22 gauge, I think) since I don't expect to draw a lot of current for interior LED's, and also because that's what I had available. If anyone knows of any reason I shouldn't have used this wire, please let me know. Otherwise, I'm just assuming it'll be fine.

Testing: At this point, all of the electrical work was essentially done, so I did some final checks before closing up. First, I reattached the connector and made sure that my ignition key light was still working. Second, I connected the new circuit to my multimeter to see how it behaves; the results are shown in the photos below.

Reassembly: After securing my new wire (used zip ties at three or four locations to make sure it didn't move around and rattle

), it was just a matter of putting everything back together.

Many thanks to Princess for providing the wiring diagrams!

Anyway, I hope someone finds this useful. I'm quite pleased with the outcome, although I haven't decided yet what kind of lighting to hook up. I guess that'll be my next set of experiments..... :wave:

Ramon · Sep 17, 2007

More photos...

First two show the connector back in place. The last three show voltage readings with the driver's door open, right after closing the door (lights dimmed), and a few seconds later (or after turning the ignition on), respectively. Turning the ignition off and pulling the key out causes it to power up again, just like the overhead map lights. Interesting that "off" was not registering 0 volts as I expected. I'm assuming that's normal.

MakingWaves · Sep 17, 2007

Great write-up and photos!

My first suggestion would be to add footwell lighting because that is really what I would like to have. It would be nice for the footwell lights to stay on after the door is closed and before you turn the key.

Ramon · Sep 17, 2007

Thanks! That's exactly what I had in mind... :yes: I have several blue LED accessory lights (Type-S variety like you find in auto parts stores), but perhaps white would look classier..... :thmsup:

MJL · Sep 26, 2007

Will led lighting work with the dimming feature that comes from the interior lights when the door is closed?

Ramon · Sep 26, 2007

MJL said:
Will led lighting work with the dimming feature that comes from the interior lights when the door is closed?

Yes. My LED's fade away gently, just like the rest of the interior lights.

kopimon · Sep 29, 2008

MakingWaves said:
Great write-up and photos!

My first suggestion would be to add footwell lighting because that is really what I would like to have. It would be nice for the footwell lights to stay on after the door is closed and before you turn the key.

I normally don't bring back dead threads, but this is a good DIY. If you want to have them stay on for a little longer, put a nice big capacitor on the line.

kaabob · Mar 10, 2009

Nice DIY! By the way, where'd you get those splice taps?

Ramon · May 2, 2009

kopimon and kaabob - Thanks

, and sorry about the late response. I haven't been following these forums as much as I used to.

The red splice taps are just the standard clamp-on ones that are available at many hardware or automotive stores (I think I picked these up at Kragen's). I used the slightly smaller ones to match the smaller-gauge wire that I was working with. By the way, it has been several months now since I did this mod, and everything is still working perfectly. It was certainly one of the best things I've done to the car. :thmsup:

RadioAccord09 · May 20, 2009

some pics of the leds uve installed?

Ramon · May 20, 2009

RadioAccord09 said:
some pics of the leds uve installed?

I hope you won't be too disappointed :sorry:, but I still have the cheap blue "Type S" LED's in the car. I originally just wanted to put them in for testing, but ended up liking the blue lighting :thmsup: so I left them in there. I find that they really complement the car's silver and grey tones, as well as my blue-themed Star Trek navi welcome screen. I installed two in front under the the dash, and two for the rear, mounted underneath the front seats, so the entire floor is basically lit up when they're on. Maybe I'll try white LED's someday (I actually already have them), but for now, blue it will stay.

tlcr1212 · Jun 5, 2009

Ramon, do the lights turn on during the daytime? I really like your idea but I'm not sure I want my LEDs on when it's bright outside...

Ramon · Jun 5, 2009

tlcr1212 - My LED's turn on and fade out along with the ignition key light and the overhead dome lights; so yes, they do turn on in the daytime. The car doesn't have a light sensor to tell it whether or not it's bright outside, so the interior lights are only controlled by things like the doors opening or closing, and the alarm arming or disarming. If you watch your ignition key light and note when it turns on and off, that's pretty much what my LED's do.

bluemoonha1998 · Jun 5, 2009

my footwells

just how i bounce may not be for you

Ramon · Jun 5, 2009

bluemoonha1998 said:
just how i bounce may not be for you

bluemoonha1998 - Nice job! I definitely like the blue lighting :thmsup:, and the idea of using an LED strip; But yeah, I think that's a little too much for me. I might consider mounting the strips under the dash so they shine down onto the floor, though. That could work for me... :yes:

starbai · Jun 8, 2009

sweeet writeup

tlcr1212 · Jun 11, 2009

Whoops I think I was thinking of the courtesy light - so do you not keep your LEDs on while you drive? Or is there a switch where you can manually turn them on once you're in the car, doors closed? The LEDs I'm looking at can be turned on and off manually, so I'm wondering if wiring it to the key ignition light will let me turn it on when I'm driving.

Ramon · Jun 11, 2009

tlcr1212 - My LED's are turned off while I'm driving, just like the rest of the interior lights. I prefer to drive without the footwell lighting, so it's fine for me. I've never actually considered the option of a manual switch.

I suppose you could do some creative wiring to bypass the multiplex controller with a manual switch if that's what you need. The only catch is that you need to wire it up so that your switch only operates the floor LED's but not the overhead lights. Just make sure that your manual switch completely separates the LED circuit from the multiplex controller (i.e., both wires are bypassed). That should ensure that the controller won't be confused (or potentially damaged?) when you manually operate the switch.

tlcr1212 · Jun 12, 2009

I'm not experienced enough to understand what you just said, forget doing it...I guess I'll be using another method. Thanks anyway, was an informative thread.

xxDaJackalxx · Jun 16, 2009

In laymans terms, if you want to be able to operate the lights manually, you probably want to avoid using the ignition wires altogether. Ramon was suggesting that, in order to still use his method of the ignition wires, you would have to put your switch before the controller that turns on and off the interior lights. Otherwise your switch will control ALL the interior lights. To avoid that, you would have to wire the LED completely separate of the interior light controller...which would be too much hassle just to use a switch.

You may want to go directly from another power source (like the car battery or stand-alone battery) and wire a switch in that way.

Ramon - Thank you for an excellent write-up. I may duplicate your efforts with hyper-white LEDs under the seats for the back floor. I hate when people get into the back of my car at night and scuff up the front seats because they can't see the floor (black carpeting). Hopefully this will help prevent that from happening.

Best mod for under $50 I've seen yet.

Interior Lighting via Ignition Key Light

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