Td5 D2 electrics - Tungsten to LED (1)

Originally written Friday 13th March 2015 when I was considering the merits and pitfalls of LED versus tungsten/halogen bulbs...

Looked online into replacing the 12v bulbs with LED equivalents. Prices are keen on the Internet and if prepared to source direct from the Far-East, it is possible to get a full set of LED bulbs for the price of two Halogen headlamp upgrades, making it well worth the effort. 

I am currently interested in the LED technology, and while the market is still a bit of a minefield, with some careful study it should be possible to upgrade easily. I well remember the effect that changing the standard front sidelight bulbs to LEDs had when I first got Hx.

Research has uncovered a problem with respect to the directional beam pattern that a light reflector can generate using conventional Tungsten 'point' source and LED 'multi' point. It's not to do with the light output in terms of its luminance, but rather the specific space inside the reflector that the light originates from.

A serious miss-match can occur particularly with dipped and main beam headlamps that will cause the projected light beam to fall short of it's requirement and in effect become illegal for road use.

This probably explains why I can't easily find LED H7 bulbs, because they are not 'type approved' by the EU or whoever. I read that the only EU approved LED headlamp fittings are the ones designed by the manufacturer from scratch to use LED bulbs. This probably equates to why at night some oncoming vehicles are annoyingly dazzling with their driving lights even though they are set on 'dipped'.

So, perhaps the only upgrade option for Hx in terms of the driving lamps is the Xenon halogen route, the so-called 'Osram Nightbreaker' set. I can see the problem with projected beam design, but feel that for other light fitments that do not rely on beam projection, the LED route is still viable. 

Well the big question is do l buy some H7 LED just to see or stay with H7 halogen and convert all the others to LED..? Here are some illustrations of the differing light fitments in use on Hx...

HEADLAMPS   -  Both of the main and dipped headlamps use a 'H7' fitting bulb.

The fitted Halogen lamps measure 44mm from the base of the mount to the glass tip and the glass envelope is 11mm in diameter. These measurements are important as the physical size of the LED cluster can at times be too big for the physical space inside the light fitment. 

The Halogens are rated at 55w but this measurement really stands no comparison with LEDS as they run at a tenth of the power.  (And even less of the heat output). The only way to compare output is to use the measurement of 'Lumens', but Halogens (or any other traditional bulb type) are very rarely measured that way. Couple this with the fact that LEDS come in differing physical sizes denoted by '3528' or '5050'.

Crucially, the LED count does not define the Lumen count, however the more LEDS there are of the same rating then the brighter it will appear. Even more crucially, the measurement shown from the base plate to the centre of the filament (25mm in the above drawing) is vital to ensure that the design of the reflector and lens produce the required light beam projection.  Compare this with an equivalent LED bulb and the 'Achilles Heel' of the LED construction becomes apparent.  Filament bulbs are 'point' source while LED is a 'multi-point'  source.

Two photos showing H7 bulbs. The shear profusion of LEDs needed to produce a comparable output is noticeable. There are 120 individual LEDs mounted but importantly, it's easy to see here that the Halogen bulb produces it's output in a very concentrated 'point' source.

Hx has tungsten/halogen bulbs fitted. I believe that fitting these LEDs would not be road legal as the factory lens/reflector is not designed for them in terms of directing the light throw onto the road ahead. 

FRONT FOG/DRIVING LIGHT

Never had to change these on Hx. They use a H11 fitting which uses a base that has a 90 degree turn built into the fitting. Some LR sources give the fitting as H10 or even H7 but I think that confusion arises from earlier D2 applications. Hx has the 'facelift' circular driving lamps mounted in the front bumper.

The actual Halogen lamp is rated the same as the dipped headlight  (ie.12v 55w ) but the physical measurements are not the same...

Once again the measurement from the base to the filament  (31.5 mm ) ensures that the fitted reflector produces the correct beam. I feel however that the fitted reflector is 'plain' as is the lens so perhaps the beam projection is not that critical in this case. .?? 

Also, I have noted that one of the lenses has misted over with condensation no doubt encouraged by the high burn temp of the Halogen bulb.

LED H11 bulbs with 68 individual LEDs. I don't have any spare equivalent Halogen bulbs so I guess these will go in when required. The biggest hassle will be getting access to the fitted lamp positions.....

FRONT SIDELIGHT / SIDE REPEATER 

This is a cap-less '501' fitting also known as 'W5W' and rated at 5w for a Tungsten element.

The glass envelope extends to the base and the two bare electrode wires simply extend beyond the base of the envelope and are bent back on themselves in the socket to make the electrical contacts. These Tungsten bulbs generate a lot of heat when running. I recall them being fitted in the auto 300tdi and indeed how the blown sidelight on Hx had heat damaged the sidelight plastic mounting making replacement tricky. 

I am currently already running LEDs in the front sidelight positions. When I got Hx it arrived with a blown front o/s sidelight and I took the opportunity to replace it with an LED equivalent. I originally fitted LEDs with a kind of 'lens' casing to spread the light projection into the lens reflector. I was happy with their appearance and performance but I soon felt that there were more powerful LEDs available in a '501' fitting. 

Two types of '501' LED.  They are polarity sensitive so I marked the positive side with some red pencil which can be seen in the above photo. The one on the right has a single LED encapsulated in a plastic "lens' although all its light is projected forward. This was the first type fitted to HX and it lasted for several months before succumbing to the vibration of the then loose headlamp unit and it began to strobe when switched on..

By then I was in a position to replace them with the 10 LED units shown above and below. Unfortunately, the heat-damaged mounting for the o/s front sidelight meant that these lamps would not fit inside due to being physically thicker. It was only a few months ago that the issue with the mounting was resolved! 

These were fitted in August 2016 and are considerably brighter then the single LED bulbs used previously. 

FRONT/REAR INDICATOR / FOG-GAURD / HIGH-LEVEL / BRAKE/REVERSE. 

Conventional bayonet capped 'P21' fitting. Also designated  '1156' or 'BA15S' '7506'. All rated at 21w and measuring 48mm tall and 26mm at widest diameter of the glass bulb. There is a single filament inside the bulb. 

Conventional Tungsten and an equivalent LED. 

These are the same LED bulbs used in the reverse light position on Hx.

REAR SIDELIGHT/BRAKE LIGHT.

Bayonet capped designated 'BAY15D'  '7528'  '1157 ' and fitted with offset pins for the dual filaments. Rated at 5w for the sidelight and 21w for the brake filament. 

Interested in how the LED versions are able to change output from side to brake output. Is it simply current altering or physically turning on more of the LEDs?  Answer, it is current related. ..

A dual filament bulb and it's LED equivalent. Note the offset mounting pins.

80 LED diodes crammed onto the surface to presumably produce the equivalent 'Lumens' 

value of a Tungsten filament.

Above chart shows the various arrangements of the Bayonet fitting bulb case... BA = Bayonet.   15 = diameter of case  (minus pins).     S= Single.   D=Double filament.    Hx uses BA15S and BAY15D. 

INTERIOR / NUMBER PLATE BULBS

These are the conventional 'Festoon' type.

All are 12v and rated either 5 or 10 watt. That is a potential 40w draw (50 if the glove box is open) on the interior lights alone! The shear reduction in current draw afforded by swapping to LEDs is not to be underestimated. 

I have replaced all these tungsten festoon bulbs with equivalent LEDs running at a tenth of the current. I was even able to select the colour of the LEDS and have used red for the main interior but also fitted additional white LEDs in there as well as in the glove box and the rear number plate lights.

Festoon bulbs come in different sizes so a careful measurement of the casing length is required to ensure correct fitting.

For the record these are 36mm festoon bulbs. The LED equivalents are available in many colours and indeed differing 'patterns' of the arranged LEDs .