98 Vectra problem blowing lights

Discussion in 'Vectra' started by Simple, Nov 23, 2004.

  1. Simple

    Simple Guest

    As above 98 Vectra, about 6 weeks ago i had to replace the passenger side
    headlamp and the rear tail light bulbs. They have now blown again (exact
    same bulbs) are there any reason why these bulbs should blow and not any
    other bulbs?
    Simple, Nov 23, 2004
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  2. Simple

    Jon Guest

    Had the same problem on my vectra. Only way to get rid of the problem was
    to replace all the bulbs in the rear clusters and all the front lights too.

    No idea how this solved the problem but it worked!
    Jon, Nov 23, 2004
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  3. Simple

    Guest Guest

    Check the altenator output voltage.
    You can do this by measuring the battery voltage while the engine is
    doing 3000rpm. Should be no more than 14.5V with the lights on.
    If it's above that figure get the battery and alternator checked by a
    Guest, Nov 23, 2004
  4. Simple

    Simple Guest

    Thanks for your replies guys.
    I forgot to mention that i had had a new alternator fitted somewhere in
    between the the time i origionally replaced the bulbs and now. Can it still
    be the same fault with the voltages as its now kicking up the same fault on
    2 different alternators?
    Simple, Nov 23, 2004
  5. Simple

    Guest Guest

    Methinks you should check the earth straps (body to battery, engine to
    body/battery) and the earthing arrangments on the front/rear lights.
    Guest, Nov 23, 2004
  6. Simple

    mikeFNB Guest

    go with that.
    earth straps!
    go over the light clusters with a fine tooth comb.

    i will guess that it is current related, the bulbs are not blowing through
    volts too high, but there is too much current passingthrough them due to an
    earthing fault, so they are blowing like fuses.
    certainly the way the rear cluster is organised.
    not sure on your exact model, but most have a wire which comes off and goes
    to the body nearby. this is just a crimp tag & a self-tapper.
    that corrodes and causes current flow problems with the eath having to find
    another route through another bilb, hence it exceeds it's wattage.

    also check the engine/gearbox one.

    mikeFNB, Nov 24, 2004
  7. Simple

    Martin Guest

    I don't think that can be right. Surely, whatever wiring failure the OP may
    have, he'll never get more than 12v (or 14.5v, or whatever the alternator is
    chucking out) across any one filament?
    Martin, Nov 24, 2004
  8. Simple

    Guest Guest

    Yes, the OP has the right idea but for not quite the right reason.
    Earthing faults can cause lamps to glow all the time, certain lamps are
    not realy 100% rated (21W brake/turn lamps for example) and can
    sometimes fail early. Other times they glow dimly
    Earth strap faults can cause the altenator voltage to rise, then bulbs
    fail. Sometime other expensive stuff (radio, varius ECU's) fails first :=(

    Guest, Nov 24, 2004
  9. Simple

    mikeFNB Guest

    who said i was talking about voltage.
    i am talking about current.
    a bulb is a fuse that glows.
    pull too much current through it and it will blow

    mikeFNB, Nov 24, 2004
  10. Simple

    Martin Guest

    How do you increase the current without increasing the voltage?

    My mate Mr Ohm said I = V / R, and I've no reason to doubt him.
    Martin, Nov 25, 2004
  11. Simple

    Mikee Guest

    tis true unless you decrease the resistance. As a filament heats up the
    resistance decreases.

    Just thought I'd throw my tuppenyworth in!

    Mikee, Nov 25, 2004
  12. Simple

    Mike Guest

    Shouldnt that read increases? (as the filament heats up)
    Mike, Nov 25, 2004
  13. Simple

    Martin Guest

    Yes it should. But even so, Ohm's law holds good (for any given R), so the
    only possible way for the bulb(s) to carry "too much" current is if they're
    defective. Which is where we came in... :-(
    Martin, Nov 26, 2004
  14. Ah My friend Mr SodsLaw says Problem with Your theory discounts problem in
    circuit,and not bulb. ;o)
    Ikie Cabolacov, Nov 26, 2004
  15. Simple

    Martin Guest

    Just how does Mr Sod reckon I can get >12 (or 14) volts across my likkle
    filament. Press the brake pedal extra hard? :)
    Martin, Nov 27, 2004
  16. Honestly If there is a slight short somewhere to the return circuit you get
    a mini coil effect
    in that area. Causing the current to rise and cook your wires.
    We once had a customer who's lights kept blowing on one side only. It turned
    out to be
    water and a slight crack in the wire causing the current to jump across when
    it rained.
    Ikie Cabolacov, Nov 27, 2004
  17. Simple

    Martin Guest

    Humph - you've stumped me. I can understand that you might get spikes, if
    there's something inductive in the circuit and you have a dodgy connection
    making and breaking. Is that what you mean? But surely in a "steady state"
    situation, the max p.d. across any two points (including a filament) won't
    exceed the battery (or alternator) voltage? Or am I missing something else?

    BTW, I've just crossed Mr Ohm off my xmas card list :-(
    Martin, Nov 27, 2004
  18. Yes your right but I find 90% of lighting problems due to either water or
    corrosion caused
    by water and the said coil effect.
    Because the short caused in this way seems to cook whatever is nearest.
    The filament or the fuse.
    I normally drop the fuse rating in problems like this to save the bulbs
    until you find the cause.
    I once had a Mini van years ago that caught fire because of the lighting
    wires rubbing on the brake lines.
    Despite being protected by the fuse!
    Ikie Cabolacov, Nov 28, 2004
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