quattro digest, Vol 1 #4713 - bulb life

Larry C Leung l.leung at juno.com
Thu Mar 13 21:15:07 EST 2003

Although some will differ in my opinion, IMHO (haven't
put this to an O-scope, as I don't have one), the output
of any auto alternator has spikes and troughs, which
pulse the bulb filaments, eventually shortening bulb
life. The battery acts as a giant capacitor, smoothing
those pulses. Wire your +12 to the battery, rather than
directly to the alternator, and perhaps your bulb life
will improve. Everything else you've done is spot on.


> Date: Thu, 13 Mar 2003 09:08:52 -0500
> From: MTNBykah at aol.com
> To: quattro at audifans.com
> Subject: Headlight bulb life
> I finally got my H4 euro's installed on my 4kq not too long ago, and
> I can =
> finally see where I'm going.  They are a huge improvement.  The only
> thing =
> is that the bulbs are only lasting about a month or so.  I have to
> buy the =
> third set today because both bulbs went (at different times)
> yesterday.
> The first set were no-name ones so I got Wagner
> super-something-or-others f=
> or about $10 each at the local parts store.  These were actually
> really goo=
> d and the beam pattern was crisper than the first set.
> The way these are wired, there is heavy gauge wire from the alt
> (fused) to =
> a separate relay for each high & low beam triggered by the old
> wiring from =
> the switch.  They are grounded with good size wire right to the core
> suppor=
> t=2E
> Is there some issue with the way they are wired?  Or can I get
> better bulbs=
>  somewhere?  The old lights really sucked, but I used to scrounge
> used 9004=
> 's and they'd last 6 months or a year.  Or do I have some other
> voltage / c=
> urrent issue or something?  Please help.
> Thanks,
> -Dan  (Boston)
> 87 4kcsq 197k mi H&R, Boge, H$ Euros
> Cross drilled Brembos, etc.

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