A4 headlight bulbs

[Andrée-Anne Bourgeois]

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. 

Louis-Alain