quattro digest, Vol 1 #4713 - bulb life

[Huw Powell]

> 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.

While there is a certain intuitive appeal to that logic, we must keep in
mind that there is a very heavy gauge wire directly connecting the
alternator output post to the battery (except perhaps in a
long-neglected type 44...), providing a *very* low resistance path to
damp those spikes (and troughs).  Far lower resistacne than through the
headlight filament circuits.

But still, as you say, a certain lack of quantitative data leaves us
both theorizing in the dark.  A lack of imagination for rephrasing at
the moment has me leaving in that awful pun, so please accept my
apologies in advance.

It would be nice to see a scope reading of the voltage at various points
on the harnesses of various cars in various conditions of upkeep and/or
neglect...

--
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/