Illumination wire?

Discussion in 'Lighting Discussion' started by SurrealOne, Jan 20, 2013.

  1. SurrealOne

    SurrealOne Former Member

    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?)?
  2. zigger215

    zigger215 New Member

    What illumination wire? I think you're talking about the dome light?
  3. Pikey

    Pikey Moderator Staff Member

    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.
  4. Enkeiavalanche

    Enkeiavalanche Moderator

    What are you hooking up?
  5. SurrealOne

    SurrealOne Former Member

    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.)

    overhead_switches.jpg
    Last edited: Jan 21, 2013
  6. zigger215

    zigger215 New Member

    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!!
    Last edited: Jan 21, 2013
  7. Pikey

    Pikey Moderator Staff Member

    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?
  8. zigger215

    zigger215 New Member

    So it is grey, did your book say whether is was a negative or positive trigger?

    Pikey, did you order your HIDs?
  9. SurrealOne

    SurrealOne Former Member

    @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:
    overhead_panel_filled.jpg
  10. Pikey

    Pikey Moderator Staff Member

    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
  11. Enkeiavalanche

    Enkeiavalanche Moderator

    Gotta say those are some Nice looking Switches.....
  12. zigger215

    zigger215 New Member

    It's not a "reverse ground". That doesn't even exist. It's a negative trigger meaning the power is constant but the impedance to ground fluctuates which causing the dimming in the lights. The symbol you're lookin for is "-". Just like our parking lights.

    Having worked professionally in the mobile installation industry and now as an IBEW wireman who has done tons of PLC installations, I can say they are nothing like cars....
  13. SurrealOne

    SurrealOne Former Member

    Pardon my fumbled terminology.

    Pikey, I'll let you know when I test -- should be this weekend, weather permitting.
  14. Pikey

    Pikey Moderator Staff Member


    I looked at the diagram again and it does not have any indication. I also looked at the parking light circuit diagram. It did not indicate a negative trigger either. Maybe the publisher "forgot" that part.
  15. zigger215

    zigger215 New Member

    Pikey I can tell you from years and years of experience that these trucks have many "negative trigger" circuits, park lights being one of them. Apply 12v to the grey/black wire on the switch and watch the free fireworks show...
  16. zigger215

    zigger215 New Member

    image-3756424970.jpg
    There you go, that's what a negative trigger looks like on direct wire. This is a complete schematic (way more in depth than a Haynes book) for a 2004 silverado.
  17. Pikey

    Pikey Moderator Staff Member

    Oh, I am not doubting you in any way. I am just stating that my manual does not indicate the (-). I would always use a multimeter to figure out what was going on before i attempted any mods/repairs on an electrical system. I have seen way too many inconsistencies in wiring diagrams to trust anything 100%
  18. zigger215

    zigger215 New Member

    That's also pretty dang true. Always double check with a meter, I second that. I will say, GM has been awesome with their consistency on our trucks, I always loved working on our trucks when they came in the shop. I always knew what I was getting good or bad
  19. SurrealOne

    SurrealOne Former Member

    I decided to go for a connection at the dimmer switch in the cab just because it's a place I knew I could easily probe. After removing my sound deadening material, cutting new material to fit (for when I finish), and probing/testing with a multi-meter, here's the verdict:

    The wire (at the dimer switch) is brown with a white stripe and is NOT a negative trigger.
    Last edited: Jan 27, 2013
  20. Scooter

    Scooter New Member

    Hey Zigger what app is that on your phone?

    Hey surreal I always love your work, I know you said 85 bucks for just the four switches but what did the whole setup run you. And would you be willing to do another similiar?

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