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Head light bulb keeps blowing

  • 02-12-2013 8:11pm
    #1
    Registered Users, Registered Users 2 Posts: 546 ✭✭✭


    Hi lads,

    Odd problem.

    I had a dead dipped beam last week. High beam worked.
    No worries, the bulb was the original and 3.5 years old. Replaced it with the same part (Philips Premium H4)...but it blew again after riding 20 meters.

    Cussed at Philips for a bit, then replaced it with a fancy Osram Nightbreaker H4 Plus, tested it, works great, started the engine... and it blew!

    Points to note:

    - They only blew while the engine was running (coincidence?)
    - Only the dipped beam blew, with high beam continuing to work (except the Osram, which blew on then the other quickly)
    - The bulbs flashed bright for a fraction of a seconds before blowing
    - All other bulbs are working fine... including the daytime running light

    I bought a handful of 75c H4's to diagnose the issue (can't afford another Osram going!)

    Any suggestions?


Comments

  • Registered Users, Registered Users 2 Posts: 2,057 ✭✭✭irish bloke


    fleet wrote: »
    Hi lads,

    Odd problem.

    I had a dead dipped beam last week. High beam worked.
    No worries, the bulb was the original and 3.5 years old. Replaced it with the same part (Philips Premium H4)...but it blew again after riding 20 meters.

    Cussed at Philips for a bit, then replaced it with a fancy Osram Nightbreaker H4 Plus, tested it, works great, started the engine... and it blew!

    Points to note:

    - They only blew while the engine was running (coincidence?)
    - Only the dipped beam blew, with high beam continuing to work (except the Osram, which blew on then the other quickly)
    - The bulbs flashed bright for a fraction of a seconds before blowing
    - All other bulbs are working fine... including the daytime running light

    I bought a handful of 75c H4's to diagnose the issue (can't afford another Osram going!)

    Any suggestions?

    Check bulb terminals for spike in DC voltage and current when switching engine on and off


  • Registered Users, Registered Users 2 Posts: 546 ✭✭✭fleet


    Will do... and it's an electrical fault I expect... I find it odd that it's just affecting one bulb though


  • Registered Users, Registered Users 2 Posts: 546 ✭✭✭fleet


    Right - figured it out :-)

    Regulator Rectifier was shot.

    Got 20V+ at 5000 revs on the multimeter when measured at the battery!

    I'm surprised it was only the bulbs that blew. The computer is fine.
    Battery is pretty screwed though!

    Weird thing is, the damn Dealz €1.50 for a set head lamp is still going! Damn thing grew an extra glass appendage but both beams still work even after hours and hours of high voltage! Think I'll leave it in!


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