A4 headlight bulbs

[Kent McLean]

Andrée-Anne Bourgeois wrote:
> OK I'll take the ball.
>
> Q1. Do headlight bulbs fade over time? I believe sealed beam headlights do.
> What about halogen bulbs? HIDs?
>
> **** To my knowledge, no. Lenses are getting less transparent over time
> (plastic much more than glass), but halogen bulbs are on-off device. They
> work or they don't.
> But, halogen bulbs are very voltage sensitive (output will get weak if
> voltage drops by just 1 or 2 volts). HID are less sensitive because of the
> ballast, all they need is 9 to 14 volts to produce 100% output.
>
> Q2. (I feel like such a newb...) Since the A4 bulbs are problematic to get
> to, is there an easy way to tell what you have (halogen vs. HID), short of
> removing the headlamp assembly to get to the bulbs?
>
> ********HID are easy to identify : they start slowly (rather like a
> fluorescent tube in your office), and then get brighter after 2 or 3
> seconds. Halogens are 100% in the first second. More, usually, there is two
> telltale : first is the fact that the HID lens must be plastic, second is
> the presence of an automatic leveling system that works on each start-up.
> The latter is not mandatory anymore on newer cars, for a reason that I don't
> know. I've seen recent Miatas and Jettas with HID and no leveling systems
> but still plastic lenses.
>
> Q3. Any recommendations on brands (that I can find at my local NAPA)?
>
> *******Brand is irrelevant if you have foggy lenses or a drop in voltage.
> I've just replaced the alternator in my urQ, now voltage is around 13V at
> the gauge, and my headlights are brighter than ever even if the old
> alternator was not dead. It was just weak for many years of duty.

Merci.  The lenses seem clear, not frosted, not yellowed, not pitted. The
bulbs are working. Maybe it's time to relay the headlights in the A4. That,
or polish the lenses. Or both.  They seemed to be aimed properly, based on
pulling up to a wall and comparing output of each side.

-- 
Kent McLean
1999 A4 Avant, V6 Tiptronic
1990 200 Avant mit V8 conversion
gone: too many to count, including my first, "Bad Puppy"