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Thread: Dash lights: 2 dimmers?

  1. #1
    Boydster's Avatar
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    Dash lights: 2 dimmers?

    Background: RF complete kit harness into Speedhut Cobra gauge kit.

    I've seen Jeff's tips on wiring Speedhut to RF, and it got me 90% of the way there, but...

    1 white power wire from F5 headlight switch ("dash lights") connects to Speedhut inverter white wire.
    F5 headlight switch dash lights dimmer is now feeding the Speedhut inverter via this white wire.
    Speedhut inverter has its own dimmer.
    2 dimmers in series? Can that even work?

    I already have the F5 headlight switch installed, do I need the Speedhut dimmer?
    I figure 2 options:
    1. Cut out the SH dimmer by cut and connect, using only the F5 headlight sw dimmer... or...
    2. Leave the SH dimmer all the way bright and just tuck the SH inverter dimmer back into the panel. :/

    I dont really want 2 dimmers for the same thing... stinks of poor planning and execution.

    I somehow dont think the SH inverter will like seeing a variable voltage input... the directions do call for 12vdc input to the inverter.
    So if I have to use the SH inverter dimmer, what do I do with the headlight sw dimmer? Just leave it on full bright? What happens when I want to turn on the courtesy lights? (dimmer goes full CCW).
    Perhaps remove the white wire from the headlight switch connector and feed it off... parking lights?

    Also, SH wants the needles to be full bright all the time, I get it, guess that means inverter white and needle white should NOT be connected together (headlight sw dimmer would also be dimming the needles) and perhaps drive the needle lights off the brown gauge feed?

    Anybodies help will be appreciated... perhaps I'm way over thinking this whole thing, but I want it to be right and operate correctly.
    ---Boyd---
    MkIV #9042 build thread
    www.boss427.us
    427W, TKO600, Moser 3.55 rear.
    Delivered Feb 2017, Graduated Nov 4, 2019

  2. #2
    Senior Member edwardb's Avatar
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    Don't overthink it. Not a big deal. The Speedhut gauge backlighting is an electroluminescence panel and requires AC from the provided inverter and will only dim with the provided potentiometer. The needles are LED and don't dim. With the RF dash lights wire attached to the two Speedhut white wires the headlight dimmer function basically just becomes an on/off switch. All the way CW, the backlighting and needles will turn off. Turning it just a little CCW, and it's enough voltage to light both the needles and the backlighting to full brightness all the way to where the courtesy lights go on and off. Apparently both the backlighting and needles don't need the full 12V DC to function at full brightness.

    In summary, use the courtesy light function as it's designed. With the knob twisted all the way CCW. Twist CW enough to turn the courtesy lights off and leave it there the rest of the time. Adjust the backlight dimming with the Speedhut knob. The needles are either on or off.
    Last edited by edwardb; 09-20-2017 at 07:07 PM.
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  3. #3
    Boydster's Avatar
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    Quote Originally Posted by edwardb View Post
    Don't overthink it. Not a big deal.
    Yeah, I tend to do that sometimes.

    In summary, use the courtesy light function as it's designed. With the knob twisted all the way CCW. Twist CW enough to turn the courtesy lights off and leave it there the rest of the time. Adjust the backlight dimming with the Speedhut knob. The needles are either on or off.
    Gotcha... cool. Thats the answer I needed. Thanks. Onward!!
    ---Boyd---
    MkIV #9042 build thread
    www.boss427.us
    427W, TKO600, Moser 3.55 rear.
    Delivered Feb 2017, Graduated Nov 4, 2019

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