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Dash lights (let's give it another try...)

Discussion in '365 GT4 2+2/400/412' started by raemin, Apr 24, 2019.

  1. raemin

    raemin Formula Junior

    Jan 16, 2007
    317
    Lyon (FR)
    Full Name:
    R. Emin
    I 'am on my third attempt on the dashboard lights!Looks good now.

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    Vidéo:
    https://streamable.com/s4q0l

    Initially I installed some leds but these were not bright enough (much better than stock), the beam was so-so (all the lateral leds are useless given the design of the gauges), and the colour a bit blueish. On top of it these would not easily fit without some persuasion (had to butcher them a lot).
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    As a second attempt I reverted back to higher output regular bulbs and upgraded the rheostat windings with thicker nichrome wire (Ni80 available in most e-cigarette shops). The illumination was quite nice but once factoring for the numerous bulbs (10) the amp-draw was quite high and I was afraid the heat would damage the 40 years old gauges. That's a good solution for whoever wants to keep the car stock though.

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    As a third attempt I gave leds another try. This time I decided to build my own bulbs: unlike BA9S, G4 bulbs are offered in numerous sizes and outputs, the idea was to fit these onto "BA9S Lamp Bases Socket". So I selected some 90 lumens dimmable leds (that's theoretically 10 times the power of the stock bulbs, much less in practice).

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    Please note that if you do not want to do the soldering job, some "G4 BA9S converter" can do the trick, but the overall length is slightly longer, so this could be a tight fit.

    I've left the instrument pinnacle enlightened for 1 hour at 75%power, no significant heat. My only issue left is to find a proper dimmer that modulates the positive wire : the ones I bought are modulating ground which is a problem as ground is shared with other elements of the dashboard and I want to keep the wiring stock.
     
  2. Jasonberkeley

    Jasonberkeley Formula 3
    Silver Subscribed

    Apr 23, 2017
    1,025
    New York, NY
    Full Name:
    Jason Berkeley
    You should sell ready-to-install kits once you've got it all sorted outed!
     
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  3. raemin

    raemin Formula Junior

    Jan 16, 2007
    317
    Lyon (FR)
    Full Name:
    R. Emin
    I've finally found a UK shop that is providing an excellent dimmer that properly adjusts the positive line. The frequency is sufficiently high so as to dim the light a lot (the chinese one I tested before was more like 66%-100%). It has a few drawbacks though: as this is a marine/waterproof unit it is quite bulky, and costs 20 times what I've paid for its Chinese sibling.

    As I did no want to butcher the original harness, I made a specific harness that can be easily tapped on the FastOn connectors of the instrument cluster. This additional harness uses the same color as the original yellow/white wires (and the same connectors obviously), so this looks more or less stock. Finally As the dimmer will be installed in the dashboard, (not on the pinnacle), I also added another 4pin FastOn Connector so as to be able to "split the harness" and remove the pinnacle without removing the dimmer.

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    Quite happy with the result. The only issue I can think about is the counter-clockwise rheostat, while the potentiometer used for this dimmer is a 2pin one, i.e clock-wise only. Finding the proper diameter, length and resistance has been such a pain that I think I will make it do with clock-wise adjustment!

     
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  4. raemin

    raemin Formula Junior

    Jan 16, 2007
    317
    Lyon (FR)
    Full Name:
    R. Emin
    Sorry for the poor video quality. Made a better copy on streamable: https://streamable.com/2s1fn

    Once I have some time I'll write down my full shopping list for whoever wants to make his own dimmable led lights.
     
  5. samsaprunoff

    samsaprunoff F1 Rookie
    Silver Subscribed

    Jun 8, 2004
    2,974
    Edmonton, AB Canada
    Full Name:
    Sam Saprunoff
    Great job on your lights.

    As for the dimming... The issue here is not really related to the switching frequency, but our human eyes. Our eyes do not see brightness linearly, but more logarithmically. Consequently,setting the dim level to 50% does not translate 50% less brightness in our eyes. To compensate for this the dimmer must have some smarts designed in to accommodate and so cost more.

    Cheers,

    Sam
     

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