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Thread: Want to know why LEDs don't work well in speedos on late models, answers here

  
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    Want to know why LEDs don't work well in speedos on late models, answers here

    Well I've finally got round to taking my existing clocks apart after mucking about with a set of turbo clocks for a while.

    I'm sure everyone here knows the problem. You fit some nice new blue LEDs and you can't see squat anymore unless it's pitch black outside. You try one in the mileage display and suddenly it dissapears even when it's dark. Want to know why? well so did I so I decided to compare a set of turbo clocks that seemed to be ok against a set of 140mph clocks from a 52 plated Mk4.

    Are they different? yes by very small amounts but it's these that cause the problem. I'd noticed when I removed the existing 140mph clocks that the mileage display seemed to have an orange edge just behind the metal framework. However at the time I couldn't figure out how to remove the needles to get to it. Even put a post up on the forum to see if the needles came off and no one at that time knew.
    So I put a blue LED in the mileage display, it was CRAP with a capitol C. It was so bad I had to put the white bulb back in. I'd tried the same blue LED in the mileage display of the turbo clocks and it worked fine. So what's the difference, well the difference is that the later clocks have had a small yellow filter installed between the glass display and the bulb. You can put a 100w blue bulb in that sucker and it's just coming out green if your lucky. Solution!! take it out, is it easy?, erm not really. I can describe how to do it if you wish but it's complicated but it's doable if your willing to try it.
    This is the little sucker that causes the problem

    It's the middle piece in case your colour blind the left hand one is the glass of the display, the right hand piece is actually a small piece of hardish rubber that connects the glass to the circuit board. The bottom piece is the frame the mileage display sits in.

    So mystery solved for the mileage display. So why are the clocks so bad at lighting up blue. I was convinced it was the light prism that causes the problem, it has changed between the 2 models, the turbo clocks have a frosted light prism, the 140 clocks have a clear prism with small light bands running through it. Comparing the 2 lit up with the same blue LEDs shows the turbo one allowing a better spread of light but it's not the problem. So what's the answer, well I was stumped for a while until I looked at the dial facings. There are markedly different. The turbo clocks are almost transparent, the 140 clock facings aren't. They are multi layed and one of the layers is our friend the yellow one. So any blue light trying to get through that is going to have a hard time, here's what it looks like.


    That's the reverse side, it's quite clear when you see it isn't it. It appears that Vx changed the facia around 2000 so if you can find an old set of clocks nick the facia plate.

    I dismantled both sets of clocks and made a set of clocks that was a mix of the turbo and 140 clocks, they light up a nice shade of blue, it's nice to be able to see what speed I'm doing at night, the mileage display is also blue and I can see it in daylight

    Well that's it, I've talked enough.
    52 Astra G 1.8, 18" Mille Miglia alloys, 325mm Brembo 4 pot conversion, Coupe leather interior, Raid strut brace, Whiteline rear ARB, Irmscher bits (skirts, Carbon steering wheel, Bonnet extension, M3 mirrors, boot & roof spoiler), Reiger Rear Diffuser & Front Bumper, Koni Adj. dampers, 35/30 Vogtland springs, Duplex quad exit ASCAR stainless exhaust.

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    nice find mate well done it sounds a bit hard to me though.

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    great research!!

    do the earlier turbo faces look the same as your new one's? surely if you have the clocks dismantled it cant be too difficult to remove the orange filter?

    this is a good find...vaux could have made our lives easy by using an orange bulb!

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    Excellent investigation ! Interesting reading.

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    Quote Originally Posted by dr_shabzzz
    great research!!

    do the earlier turbo faces look the same as your new one's? surely if you have the clocks dismantled it cant be too difficult to remove the orange filter?

    this is a good find...vaux could have made our lives easy by using an orange bulb!
    I should have taken a pic of the rear of the turbo facings as well for comparison. They look the same as the others but imagine them as just the white bit but without all the coloured layers, you can't even see the numbers through them as the numbers are printed on the other side.

    Getting to the mileage display means dismantling the clocks entirely, circuit board out, needles off etc if you've got the needles off to fit a new facia then I'd say do it, it's not difficult just fiddly. I have the old clocks around so I could do a How-To if you'd like, the hardest part of the entire thing is removing the needles, they can be a bitch to remove and it's scary as your semi convinced they will break before they come loose. I had a little trick to removing them which worked a treat on the turbo clocks but didn't work on the 140mph ones, I had to divise a new method.

    You can't beleive the mileage display uses rubber as an electrical contact but it does, very weird.
    52 Astra G 1.8, 18" Mille Miglia alloys, 325mm Brembo 4 pot conversion, Coupe leather interior, Raid strut brace, Whiteline rear ARB, Irmscher bits (skirts, Carbon steering wheel, Bonnet extension, M3 mirrors, boot & roof spoiler), Reiger Rear Diffuser & Front Bumper, Koni Adj. dampers, 35/30 Vogtland springs, Duplex quad exit ASCAR stainless exhaust.

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    Brett's Avatar
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    so early sxi sri white faced clocks should befine but my 02 plate ones are mostlikley them because the millage is a bitch to see

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    Fraid so Brett but at least you know how to fix it now. I'd be interested to know whether the 140 white faced facia has the multi layered one as well as the black faced one so if you ever put them apart let me know please.
    52 Astra G 1.8, 18" Mille Miglia alloys, 325mm Brembo 4 pot conversion, Coupe leather interior, Raid strut brace, Whiteline rear ARB, Irmscher bits (skirts, Carbon steering wheel, Bonnet extension, M3 mirrors, boot & roof spoiler), Reiger Rear Diffuser & Front Bumper, Koni Adj. dampers, 35/30 Vogtland springs, Duplex quad exit ASCAR stainless exhaust.

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    Great research!

    Looks like I'll be sticking with yellow clocks from now then! Bugger!!!
    2006 Astra VXR on 19's in Arden Blue
    ExhaustsUK Catback, Eibach Sportlines, DS Ultima, Roose hose kit, Forge recirculating dump valve, Full self modded SMD conversion

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    norm29's Avatar
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    which ones are pictured ken? as last night i stripped a set of 888 dials from an 02 reg 888 and they were the ones with the gunmetal surround. they didnt have the yellow filter.
    im now in the process of painting a spare surround and replacing the red needles
    Car broken- A3 170 quattro s-line

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    So can someone clarify something for me....
    Are the turbo dials 160mph? Same as the 2.2 coupe?
    I'm thinking of having white dials with blue mileage display and blue mdf.

    how easy is it to change the needles? I want to replace my normal black ones with red ones - like the linea rossa...

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