Instrument back lights

Discussion in 'Mech Tech' started by stirlingmoz, Nov 14, 2018.

  1. stirlingmoz

    stirlingmoz Supporter

    I drove my crewie for the first time at night yesterday.

    Even with the rheostat on the switch turned right up, the speedo backlighting is very poor making it difficult to read.

    It’s worse on the right side half of the speedo which is in darkness.

    Are the aftermarket LED back lights any good ?

    Any recommendations ?


    Stirlingmoz
     
  2. You could swap the instrument bulbs for LED ones (sounds like one of your bulbs has blown anyway). Will definitely improve things. Or use use LED strip stuck to the backplate - bit more complicated.

    Even with 2W bulbs in, VW's panel illumination was pretty carp.
     
  3. davidoft

    davidoft Sponsor

    Are all the bulbs working, sounds like not, personally find led etc way to bright
     
    Lasty and snotty like this.
  4. mikedjames

    mikedjames Supporter

    LEDs can be used everywhere except the alternator warning light and sometimes the indicator warning light (some flasher relays buzz instead of working)

    However LEDs can be too bright and greenish or varied in colour and brightness if you buy the cheapest eBay ones. I ended up buying two batches, discarded the first one and half of the second one just to get them all about the same sickly colour.

    And the dimmer does not work properly because they draw less current so the dash lighting circuit cannot drop as much voltage across the series connected dimmer variable resistor.
     
  5. I changed all mine to led and found it lots better to be honest definitely not to bright.
     
  6. mikedjames

    mikedjames Supporter

    The reason to NOT use LEDs for the alternator light is that it shows two different faults.
    One is the alternator output voltage is low. This lights when the voltage on the battery is higher than the alternator. So current flows from the battery TO the alternator.
    The other fault that can kill your stereo etc is when the battery connection is bad and the alternator voltage goes high. Then current flows FROM the alternator and the light comes on again.
    Also with some regulators the initial current to excite the alternator comes through the low resistance of a cold filament bulb.
    A LED has a higher resistance than a cold 1.2watt filament bulb amd only lights up and conducts electricity in one direction. So in some cases your battery will never charge properly.
    You could use two back to back LEDs but they dont fit.
     
  7. stirlingmoz

    stirlingmoz Supporter

    Thanks for all the replies. All very useful and food for thought.

    Sadly I didn’t get any time to work on the crewcab this weekend.

    My motorbike needed a new battery and it took me longer than expected to wrestle the old one out and finagle the new one in. It takes me to work every day so needed a bit of love.

    I need to check that the lights I do have actually work but even if I bite the bullet and go for LED’s I will only use them for back lights.


    Stirlingmoz
     
  8. I found LED's looked wrong in an older vehicle, which put me off, tho' I the slightly brighter light was welcome.

    Also, the alternator on a Beetle is wired so that the current flows in the reverse direction to an LED, so as @mikedjames says, an LED won't excite the alternator. Haven't got that far on the Bay yet, but I can't imagine VW doing it differently.
     
  9. stirlingmoz

    stirlingmoz Supporter

    Just had the instruments out for a shufty at the backlights.

    The speedo right side bulb holder didn’t have a bulb in it !

    No wonder it was dark.

    Good call @davidoft

    Both bulbs working now.

    Let’s see what’s its like next time I do some night driving.


    Stirlingmoz
     
    paradox likes this.
  10. It'll be awful.
     
    77 Westy likes this.
  11. MorkC68

    MorkC68 Administrator

    [​IMG]
     
    Valveandy, Dubs and 77 Westy like this.

Share This Page