740 day running lights

Discussion in 'Volvo 740' started by Mungo \two sheds\ Toadfoot, Oct 16, 2005.

  1. A small problem: The "knackered bulb" indicator in the car is lit but goes
    off if the sidelights or headlights are switched on, indicating a fault with
    a day-running light.

    One day-running light is brighter than the other because *both* filaments
    (stop and tail bulb - 21w/5w) are lit and the other only has the 5w filament
    lit. If I turn the sidelights on then only the 5w filaments are lit, both
    sides. The bulb *looks* fine but I haven't got a replacement to hand, nor a
    tester, which is at someone else's house at the moment.

    Are both filaments supposed to be lit when the day lights are on or just the
    21w one?

    Si
     
    Mungo \two sheds\ Toadfoot, Oct 16, 2005
    #1
  2. Mungo \two sheds\ Toadfoot

    Steptoe Guest

    Hard to tell as you get reflection from the 21 to the 5 but I am sure only
    the 21 should be on; failure of the 21 is the commonest fault.
     
    Steptoe, Oct 16, 2005
    #2
  3. I'm fairly sure they were both lit but I could be wrong - it's difficult to
    look at a 21w bulb!

    If they *are* both lit any idea why this might be?

    Si
     
    Mungo \two sheds\ Toadfoot, Oct 16, 2005
    #3

  4. *Thinks*

    Dodgy wiring, switch, or holder, innit? Bugger. I hate electrics.

    Si
     
    Mungo \two sheds\ Toadfoot, Oct 16, 2005
    #4
  5. Mungo \two sheds\ Toadfoot

    James Sweet Guest

    You've probably got a bad ground connection at the light.
     
    James Sweet, Oct 16, 2005
    #5
  6. You might be right. I just got in the car and the warning light has gone
    out! It's been coming on intermittently for the past few weeks but decided
    it was staying on for good recently. Until this evening. Ho hum.

    Si
     
    Mungo \two sheds\ Toadfoot, Oct 16, 2005
    #6
  7. It is a well known fault of twin filament bulbs that when the earth
    connection doesn't quite make good then the other filament acts as an earth
    contact. The bulb itself can also fail as a Pontiac GTO owner I diagnosed
    for will tell you.

    All the best, Peter.

    700/900/90 Register Keeper,
    Volvo Owners Club (UK).
     
    Peter K L Milnes, Oct 16, 2005
    #7
  8. Mungo \two sheds\ Toadfoot

    SimonJ Guest

    A small problem: The "knackered bulb" indicator in the car is lit but goes
    Sounds like classic symptoms of an earth fault.
     
    SimonJ, Oct 16, 2005
    #8
  9. Yes, both are supposed to lit.
    I am 100 % sure, i do have the Volvo electrical diagram book for that car.
    I guess Volvo made a shortcut in the design, otherwise they would have had
    to arrange with an extra relay to turn the filament for the parking light
    off when the day running light is on.

    /aw
     
    Anders Wiklund, Oct 16, 2005
    #9
  10. Mungo \two sheds\ Toadfoot

    James Sweet Guest

    Seems they would have just arranged the headlight switch to turn off the
    small filament, that's how it is on cars without DRL, the parking lamp
    filaments are only on when the switch is in park or headlights. When I added
    DRL I used a relay to turn them off whenever the parking lamps are powered
    since my headlight switch doesn't have provisions for them, it does have
    blank spaces where more terminals could have gone though.
     
    James Sweet, Oct 17, 2005
    #10
  11. iirc they use a special bulb, NOT a stop tail (very similar)
     
    mrcheerful , Oct 17, 2005
    #11
  12. Rear lights is also on with DRL so they would have had to separate tail and
    front parking lights.

    What is the problem?

    The solution has one bonus: When the 21 W filament goes out there is still
    some light from the 5 W.

    /aw
     
    Anders Wiklund, Oct 17, 2005
    #12
  13. Mungo \two sheds\ Toadfoot

    john Guest

    yes it's normal, I had an old Saab 99 and both filaments were lit. I much
    preferred those DRL's to the permanent headlamp ones.
     
    john, Oct 18, 2005
    #13
  14. Mungo \two sheds\ Toadfoot

    Stuart Gray Guest

    My C reg 740 had double filament dlrs. the 21w lit with no other lights on
    and the 5w lit when headlights were switched on. My G & J reg used single
    filament 21w bulbs that go out with headlights on.
     
    Stuart Gray, Oct 18, 2005
    #14
  15. Mungo \two sheds\ Toadfoot

    Gunner Guest

    The Canada Safety Council disagrees with your preference and option provided
    by OEMs. They prefer normal headlights on. The purpose of DRL is help
    make an oncoming driver aware of your presence on the road. Regardless of
    the cost of the bulbs it is very inexpensive if it prevents an on coming car
    from getting in your way. An accident between on coming cars at closing
    speed of 225 KPH or 140 MPH would not be a very pleasant experience even in
    a Volvo.

    My Volvo setting is "headlights on". Day or night I do not think about
    headlights at all. One less thing to remember
     
    Gunner, Oct 18, 2005
    #15
  16. Mungo \two sheds\ Toadfoot

    Guy King Guest

    The message <>
    Though research is now being conducted into whether the unintended
    consequence of this is that drivers concentrate more on the cars with
    lights and fail to notice pedestrians and bikes. Early indications
    (IIRC) show that this is the case.
     
    Guy King, Oct 18, 2005
    #16
  17. Eh?

    I think you'll find that DRL are better than OEM headlights. Headlights are
    for when it is dark, period.

    Hammo
     
    Hamish Alker-Jones, Oct 18, 2005
    #17
  18. Mungo \two sheds\ Toadfoot

    Adrian Guest

    Hamish Alker-Jones () gurgled happily, sounding much
    like they were saying :
    Better in what way?
    No, they're for when you need to be seen, as well as for when you need to
    see.
     
    Adrian, Oct 18, 2005
    #18
  19. Mungo \two sheds\ Toadfoot

    Guy King Guest

    The message <BF7B4A06.13072%>
    That may be true in Australia, but in the UK it's different.

    Rule 201: You MUST use headlights when visibility is seriously reduced,
    generally when you cannot see for more than 100 metres (328 feet). You
    may also use front or rear fog lights but you MUST switch them off when
    visibility improves.

    http://www.highwaycode.gov.uk/21.htm#211
     
    Guy King, Oct 18, 2005
    #19
  20. Dipped light isnt designed to be seen they ar for seeing.
    This problem is obvious with Xenon lights, they have poor visibility.
    Maybe thats why Hella has introduced DRLs:
    http://www.tagfahrlicht.de/daytime-running-lights/
     
    Anders Wiklund, Oct 18, 2005
    #20
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