# Dim Headlights?



## LeTrench (Nov 29, 2012)

Hello all - new to this so do bear with me if I'm being a plank!

My headlights don't seem to be as bright as they should be - I've had my TT a month and there is a definate difference between the brightness on THIS car, compared to my old, crappy Mazda6!

(Should probably point out that its a 56 plate and done 50k miles)

This morning, my girfriend followed me to work and just emailed me to ask if the I had my lights on (which I did) as the rear lights didn't look like they were on - or weren't very bright.

Is this a known issue? Is there something wrong with my battery? Do I need Halogen bulbs? Should I just get my eyes tested and only drive in the daytime!???

Any advice would be welcome!


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## RazMan (Aug 28, 2012)

No plankness detected so carry on :lol:

Do you have xenon or halogen headlights? If the rear lights are dim maybe you have tinted lenses?


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## LeTrench (Nov 29, 2012)

I couldn't say for sure what type of bulbs I'm using without checking - however, everything on the car is standard so nothing should really be artificially tinted...

I don't suppose it will hurt to get myself some 'better' bulbs at the weekend (xenons?). I guess I was just concerend that it was the first signs of something more serious!


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## RazMan (Aug 28, 2012)

Before you start thinking about upgrading your bulbs, you need to know what type they are :lol: 
You don't mention what model your car is - a 2006 model will probably have xenons. Do they light instantly or 'spark' into life?


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## LeTrench (Nov 29, 2012)

Mk 2
2007 56 plate
2.0T FSI 2d S Tronic

They seem to light instantly - what should I be looking for??


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## igotone (Mar 10, 2010)

Xenon lights are unmistakable, tending to look very white and bright with perhaps a tinge of blue. Also if you park near to a wall or similar you should see a very sharply defined cut off point at the top of the beam, something like so....


Xenons. by tonky8203, on Flickr

Also if you start the engine up near a wall you'll see the xenon self levelling in action as the lights do a little dance and then settle at operational height.


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## moro anis (May 27, 2010)

Xenons are also automatically adjusted for ride height. If you have a manual wheel to adjust the lights, they're not Xenon if you have the wheel they are. Also Xenon lights have headlamp washers. These activate - quite distinctly, when the headlights are on and the screen washer used.


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## LeTrench (Nov 29, 2012)

Cheers peeps - looks like I have standard Halogen then....

I'll get them changed at the weekend and see if it makes a difference!!!
(Halfords are doing a 2 for 1 deal on "Super Brilliant Bulbs" http://www.halfords.com/webapp/wcs/..._10145867_zygonManPartNum_HBU477_zygonPrice_0 )


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## RazMan (Aug 28, 2012)

I can recommend Osram Nightbreakers - fantastic improvement over standard [smiley=bulb2.gif]


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## TT-driver (Sep 14, 2010)

Older bulbs, halogen and Xenon do loose their brightness over time. Upgrading to extra bright bulbs may result in a shorter bulb life. Two other things you may want to check: the voltage in the car and possible dirt in the headlights/on the lenses.

Replacing bulbs is documented in the manual (and the KB) and all tools required should be in the tool kit.


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## John-H (Jul 13, 2005)

From a previous post (ignore the HID bits if you don't have them):

HID lamps are visibly brighter when replaced after a couple of years. Although they have a ten year lifetime, they can get very dim and change colour over that time, even though they continue to work. All HID lamps are limited to 35W so new cars that look brighter are either simply due to being new bulbs or better lenses. I suspect new bulbs is the main reason though :wink:

These are new Philips D2S bulbs which are standard TT fitment and used by most car manufacturers. They are rated as 3,200 lm @ 4100K and are the brightest available at the standard 35W power rating. http://www.lamptech.co.uk/Spec%20Sheets ... %20D2S.htm










Bluer (higher K rated) Philips bulbs are available but are not as bright at only 2,400 lm @ 5,800K: http://www.lamptech.co.uk/Spec%20Sheets ... ltinon.htm

You'll find this generally - the higher the K rating (bluer) the less lumens.

HID lamps are noticably dimmer beyond two years of age, although they do "last" for years longer, getting dimmer all the time :wink: . The best upgrade for visibility is to get new standard ones!

This is the cheapest source of Philips D2S HID bulbs I've found:
http://www.hidplanet.com/philips4100k.html 
$78.99/pair + $38.92 shipping = ~£55.9104 for a pair

The cheapest UK source I've found is: 
http://www.xenonmaster.com/shop/item.asp?itemid=4

... at £35 each plus £4.50 post making a pair £73.50 - You get a 20% TTOC discount too!

*Main Beams:*

For main beam, Philips Xtreme +80% were the brightest but this has been overtaken recently by Osram Nightbreaker +90%.

If you want visibility with maximum range then don't go for anything with a heavy blue tint - that just removes the yellow part of the spectrum leaving the bulbs bluer but with less light output.

At night, human eyes are more sensitive to yellow light anyway, so that is not a good idea. In dim conditions you perceive it as white anyway as colour vision is less sensitive than black and white.

Also blue light is scattered by water vapour and absorbed more than yellow, so blue bulbs cause more short range back reflection glare and by the time the light has gone down the road there's little remaining that gets returned from long distance.

I first noticed how good the new HID bulbs were down a good mix of roads in the dark. I am now very impressed with the combination of lights I have (Philips Xtreme H7, Philips D2S HID). In fact the new D2S burners are so good that I can drive at high speed and still see far enough ahead on dip beam to cover my comfortable stopping distance! Amazing!

With main beam on, my visible stopping distance is way greater than required for the maximum speed of the car. Very impressive!

Without the brighter HID dips, the bright H7 main beam caused you to loose visibility to the sides because of the contrast giving you tunnel vision but now with the brighter dips everything is more in balance and you get an excellent even spread of visible light  .

One disadvantage is that if you come across a reflective roadsign, the amount of back reflection is dazzling and you need to switch to dip :wink:

*WARNING:* When replacing the HID bulbs, make sure your lights and ignition are turned OFF otherwise you can get a 23kV shock :!: 

*Wak's guide on changing bulbs:* http://www.wak-tt.com/tt_bulbs/changingbulbs.htm

*Some supplimentary information:*

Here's a graph of the human eye's sensitivity to light colour during daylight when the cone sensors are more active:










At night the eye is most sensitive in the green - yellow portion at around 550nm when it is using its rod sensors:










Here's a graph of "Colour Temperature" in Kelvin.










This is the spectral spread of a bulb of 5000k amd one at 7000k:










So, for the most effective night headlight vision choose 4000k-5500k bulbs. 8000k bulbs put a higher proportion of the energy in the blue part of the spectrum where the eyes are less sensitive at night, so you'll end up with poorer night vision and dimmer light for the same wattage :wink: Some bulbs also achieve a blue hue by filtering (wasting) the yellow part of the emission - another reason for having less lumens for the same wattage.

There is also the effect of water vapour in the air. Water absorbs the higher colour temperature moreso than the longer wavelengths. That's why fog lights are sometimes coloured yellow - because the yellow part of the spectrum is not absorbed as much. If you have bluer headlights and fogs they will be next to useless in misty foggy conditions - the light has got to go down the road and back for you to be able to see it - being absorbed all the way. If you want to see further don't get blue/purple higher K bulbs! :wink:

Further reading:

http://www.intellexual.net/hid.html
http://www.danielsternlighting.com/tech ... d/bad.html
http://www.motorcycleproject.com/motorc ... -blue.html

Source of discounted lamps: http://www.ttoc.co.uk/website/viewtopic.php?f=29&t=3910 Scroll down to Xenon Master


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