I'm going to tap the reverse wire at the steering column (again) next weekend and figure that while I'm at it I might hook the illumination wire. Is there a spot on the column to hook it and, if so does anyone know the colour? If not, where's a good spot to catch it on a NBS truck (and what colour is it, there?)?
What illumination wire? I think you're talking about the dome light?
no, I believe he is talking about the instrument cluster lights. I will check my diagram in the manual and see what it says in the morning.
Pikey is correct -- I'm looking for the dimmable circuit used to control the gauge cluster lights, the OEM radio lights, etc ... and I'm looking to hook it somewhere OTHER than at the dimmer, itself, as my sound deadening in that location makes the switch a beast to get to.
For this application I'd need dimmable +12v that's activated when the gauge cluster lights are activated, as I'm adding four Contura V dual LED rocker switches and a digial air pressure gauge in the overhead ... and am toying with the idea of having them on the dimmer rather than on ignition switched +12v. (For the rockers, the upper LED backlights the switch text ... and would be on this circuit along with the gauge whch supports dimming... while the lower indicator bar activates when a switch is enbled.)
Ok it's a grey or grey/black wire at your dimmer. Very very easy to get to. To test it, hook your meter up and turn your lights on, move your dimmer up and down and you'll notice a change in voltage. Remember there is also a negative trigger parking light wire at the switch, it will be the same color as the illumination wire.
Personally, I would stay away from that circuit...nothing good can come from tapping into it. Especially to power some LEDs
Update: I see what you're doing now, very nice! It would be fine to tap into that circuit for your application. If it is indeed a negative trigger like I remember, you'll wan to hook up power to 12v constant and then hook your ground up to the trigger wire. That's how negative triggers work. For the life of me I can't remember if it is or isn't. If I were home I would test it real quick for you...3.5 more weeks then I get to go home!!
The wire is grey according to the Haynes manual that I have. As I am sure you already know that you can pick it up anywhere that the lights dim. HVAC control panel, radio, instrument cluster harness, doors (not that you would want to). Those are some pretty awesome switches. Did you have them custom made?
So it is grey, did your book say whether is was a negative or positive trigger?
Pikey, did you order your HIDs?
@zigger215, thanks for mentioning the reverse ground bit!
@Pikey, I don't have a Haynes manual (I've got the Chiltons -- might have to pick up a Haynes if it's that detailed). Does it indicate if that's a reverse ground circuit, perchance? Zig's raised a good point. (If it doesn't say then I'll just test for it, next week, as it's simple enough. Let me know.)
Oh, and I did custom-order the switches. From left to right the first three are SPST twin (blue) LED switches for turning things off/on. The fourth (horn) is a SPDT switch and its intended purpose is to serve as a toggle between my regular horn and my air horn (once I get it) using the normal steering wheel horn button. The horn switch is bone stock but the other three are custom laser-etched. OTRATTW.com (stands for Over The River And Through The Woods) did them for me. Great selection and fantastic customer service ... speedy shipping, too.
However it wasn't cheap -- those 4 switches (with all the bells and whistles ... plus shipping) cost 85 clams. Said bells and whistles included the mated rear female panels (so that I can wire the panel once, mark it, and then simply plug it into the male switch to connect/disconnect all wiring) and the wire-ends to go in the panels. The accessories were cheap, really. What wasn't were the blue, twin-LED switches. Blue apparently commands a premium, and they were out of stock in November and I had to wait until 12/31/12 for the Blue LED switches to come into stock!
Also, the changes I requested to an existing switch cover (basically word/labeling changes) didn't cost anything extra, as OTRATTW laser etches each switch for each order. Kinda cool!
I posted this, elsewhere, but here's the finished overhead console unit after 4-ish hours of painstaking measurement plus dremel time:
I have wired hundreds of 4000 wire or more PLC control panels in the past few years, I have never seen a callout or symbol for a reverse ground circuit in all of the diagrams I have looked at. After the question arose I closely inspected the wiring diagram in my manual for any symbols that I have never seen before and any illogical wiring. (reverse ground would be illogical to me as I have not seen it other than on a old MGA) It looks to be a normal circuit as it show the grey wire going to a bulb and then a ground on the other side of the bulb. My manual actually only goes up to 2003. So, maybe something has changed. But, as of now everything in it has been accurate for my 2005. I would test it just to be sure. Please let me know after you test it