LEDs everywhere

A project I've been contemplating for quite some time now, and with the constant advances in LED technology, I thought the time had finally come: LEDs all around the car. Not in the external traffic lights, for sure (with one exception, I'll return to that) but inside, with the large collection (nearly a hundred, really!) of bulbs everywhere. Let's count: instrument panel, warning lights, LH and RH display, switches, A/C panel, ceiling and rear lights, gloveboox, boot, door sill courtesy, radio surround, ashtray, cigar lighters, sunvisor. Quite a lot.

The LEDs were sourced directly from China using AliExpress, giving careful consideration to previous user feedback, to minimize the risk of disappointment. I only selected items that previous users praised for their light output. Most happens to come from a store named WLJH. All the internal LEDs together cost less than 50€ in total which, I consider, is perfectly reasonable.

Instrument panel and friends

Let's start with the small W1.2W T5 bulbs. My original intention was to use 5050 SMD LEDs all around because of their larger light output (5050 simply means the size in tenth of a millimeter, so a 5050 will be 5 × 5 mm). But I couldn't find them in socketed, colored variants. You have to pay attention: T5 is the actual bulb in the socket (whether it's removable as with the tungtsen bulbs or functionally equivalent in the socketed but inseparable T5 LED bulbs). The socket itself has another standard and there are several variants: B8.3D, B8.4D and B8.5D, denoting the relative size of the small connectors. We need 3D but the 5050 LEDs on the market (probably due to size constraints) only come in the larger, 5D size.

So basically, we have two options.

  • we can use socketed bulbs with a potentially less potent LED, then we have the nice touch of having colored sockets according to the color of the LED; this helps with the replacement and later handling;
  • we can reuse our existing sockets and put standalone T5 LED bulbs inside. We lose the possibility of colored sockets and those bulbs are somewhat longer (the socketed variant can do away with the connectors of the bulb and build the two halves together).

Finally, I decided for the second option. I really liked the idea of colored sockets but the actual performance is more important.

In any case, we need the LED bulbs in the color of their function. As I experienced it when I did the internal lighting of some switches, using colored LEDs for colored display positions gives a nicer look than using white LEDs. There is less waste of brightness and the final color will be more vivid and pleasing. Using white LEDs will result in washed out colors.

And there are places where we need the socketless, standalone bulbs anyway: around the radio, in the suspension and ignition switches.

We have two options: either these colored bulbs, more reminiscent of traditional bulbs, with their connectors formed of thin wires, or the PCB-based counterparts. These second ones look a bit strange (and come without color markings, but you can help yourself by marking them on the edge with colored permanent marker pens) but have two distinct advantages. First, the connection in our sockets in much more reliable, due to the much larger contact area. Second, they are a bit shorter and we have a few places where this counts.

In both cases, it pays to prepare everything first on the table, with a voltage source of 9–12 V. With the wire end bulbs, you often need to bend the wires to the outside to make them work in our sockets. When it's lit, place a little mark on the bulb housing on the positive side with a permanent marker (preferably in the color of the LED in the case of the PCB-based version). Later, when you install them in the car, use the following diagrams. Note that they show the position of the positive contact when you insert the socket into the hole, not after twisting it. In case of the PCB-type bulbs, if you feel it's not that easy to fit them into the holes, you might need to chamfer the corners of the PCB very slighty with a small file or sanding paper.

It's more complicated than to replace everything with LEDs, though. First, the airbag warning light circuit doesn't tolerate LEDs, so V1 should be left as a traditional tungsten bulb (with LED, it keeps blinking constanly, warning of an airbag problem). Second, the nice glowing orange gauge pointers depend on a specific kind of backlighting. V20 and V24 are most reponsible for the pointer illumination but V17 and V22 also take part. T5 white bulbs are of the cooler white variant, lending a bluish tint to the pointers: better than nothing but still not ideal.

Additionally, V18 and V19 are there for the turbo gauge, so if you don't have one, you don't need to put green bulbs there (it would create a much brighter background at the bottom of the tacho). Still, you can use those positions with less bright LEDs to help the orange pointers. This is something you really have to experiment with to find the best solution for your own needs but my current setup is:

  • a yellow LED in V18; this helps the tacho pointer without adding a visible hot spot in the tacho left corner,
  • a traditional tungsten bulb in V19; this helps the redline marking without adding a visible hot stop in the tacho right corner, and provides good illumination to the pointers,
  • a traditional tungsten bulb in V24; this feeds mostly the pointers and doesn't add a very visible discoloration to the green backround there.

There are other things to consider, too. Due to the way these colored LEDs are manufactured, there are brightness differences in color, even if the bulbs are externally the same. White and green are always the brightest, blue is OK (we only need it in a single position, anyway) but red and yellow are dimmer, no matter what. Yellow is also a bit orangeish to start with. So, there might be another workaround for the yellows: a less potent LED but in white:

It's less bright than the 5050 chips described earlier but it's white, so the brightest color of the game. If we forget the original idea of same color as the warning light position in this single case, it will be less orangeish, more yellowish in shade and just on par with the other warning lights. But this might be a question of personal preference, too.

Warm white would be even better but I've never seen these T5 bulbs in warm white.

The rest are green everywhere. The suspension switch has a really small confined are inside, so the illumination effect of the LED is very strong and nice, even in daylight. The two buttons beneath the radio are acceptable but the coloring is not absolutely ideal. This is the place where the shorter, PCB-based bulbs perform better:

Display background

The displays (LH, RH, A/C) use the same bulb but I found an even better solution. There are T5 LEDs sporting two large 5730 SMD LEDs on both sides. They might look strange at first being based on a PCB but they fit into a T5 socket nicely. They are excellent in places where there is a need for a uniform, large display background rather than a spot-like, local illumination. All three displays mentioned above are perfect locations. Instead of local light, they flood the entire display compartment with enough light to give a nice, uniform background effect. The left on the picture is perfect in layout but, unfortunately, only comes in cool and warm white.

The right one is a bit more interesting because it has a third LED on the front that we don't need (it would cause a very strong hotspot). I was lucky with this bulb because its chips are on separate circuits. I simply desoldered the front chip and the remaining two went on working. With a different bulb you might need to replace the chip with an appropriate resistor, though. So, using the second variant requires a bit of work but the end result is better: it's slightly less bright which is an advantage here (we only want the actual characters to be lit, not the background) and it can be bought in green. And if you find them still too bright, you can even desolder one more side chip. leaving only those facing the center of the display unit (but try experimenting with tape covering the LEDs first before you grab the soldering iron).

The RH display has two or three light bulbs depending on the variant, the trip computer version has one more than the simple clock. But with three such side illumination LED bulbs, we already overdo it. I found two (center socket simply left empty) to be better. Thanks to the side lighting capabilities of these bulbs, there will be no ugly darker center spot.

The only temporary problem I faced was in the A/C panel: the bulbs are a bit long and don't fit there. But then came the Aha Moment: cutting pliers! The connector end of the bulb is quite long, as you can see on the picture. Cutting about the third is the solution in the A/C panel. Still long enough to be housed in the socket properly and there will be not problem with fitting. And the display is just beautiful, just like in the LH display:

Apart from these displays, they are also my bulb of choice in he ashtray and cigar lighter positions where there is room and the principal direction is to the sides, not to the front. However, we'll have a little trouble with the cigar lighters. All other T5 sockets have connectors arranged on the opposite sides (left and right). The cigar lighters, unfortunately, have it on top and bottom. This means an immediate and sure short circuit if you insert a PCB-type LED bulb here (the manufacturer could get away with this stupid solution in the case of wire ended tungstens). You need a bit of insulating tape to cover the diagonally opposite connectors (say, right connector on both sides) of the small bulb, there is no other solution.

And finally, this is the perfect LED bulb for the ignition switch lighting as well. Don't try to force it open in the middle, the brown connector part and the white cylindrical cover is glued together. Prise off the black end cap instead and use needle-nosed pliers to remove the original bulb. A white two-sided LED bulb will be perfect here, too.

Internal lighting

Most of the internal lighting uses T10 W5W bulbs. Two in the ceiling spots, four for the rear seats. There is one in the glovebox, one in the boot and four in the door sills. I found several possible LED bulbs. The most logical one has 5050 LEDs all around to give a 360-deg light pattern, while the other is a beast of lots of 3014 chips on both sides:

The second proved to be more pratical in the glovebox, the boot light and the door sills. In these lamps the principal direction of the light is to the sides, so the flat bulbs perform excellently (note that all these pictures were taken in broad daylight, just in the shade of a door or similar, to show the real results. It's too easy to make very bright looking pictures with today's overautomated phone cameras).

The map reading lamps in the ceiling are fine with the 360-deg bulbs (again, note the daylight, there is a usual shade behind the windscreen, that's all). I know it's a question of taste but I really like this pure white instead of the old tungstenish yellowish tint:

But the same bulbs would be to bulky in the rather shallow lamps of the rear seats, we need a different format there.

And it wasn't my intention to replace the halogen bulb in the ceiling lamp but I was clumsy enough to drop it while hot and this is not something bulbs like. This BA9s socketed bulb being a one-trick pony in the XM, I didn't even have a spare, so I looked it up in the store finally. It will match the map reading lights now (if you compare them, they are the very same LED bulbs as the T10 ones, just with a different socket):

The result is also very good here. The T10 bulbs for the rear seats could be just a bit more uniform but with the limitations of this shallow design, they perform still rather well:

The internal lights are driven from a timer circuit that dims them gradually rather than switching them off abruptly. I'm happy to report that this function works well with LED bulbs, too. This is important because there were some speculation earlier whether the different characteristics of LEDs would allow dimming or not, whether they would be switched off rather abruptly or not. In reality, although the timer interval is very slightly shorter than with the original tungsten bulbs, the dimming effect remained.

Sun visor

This is less important in brightness, the benefit of chips would be more in the cooler operation. Almost all festoon LEDs, in order to achieve a brighter ouput, have the chips on a protruding platform in the middle, which is not acceptable for us because of lack of space. So, I chose the newer, COB LED variants that actually look much like the old filament inside the glass housing (we need the size of 36 mm):

Let's see everything compiled into a table for easier overview. Note that the quantities show more than actually required. Stores sell these bulbs in lots, so I had to round up to the next possible amount. Also, I wanted to have plenty to spare, who knows, in spite of the usual life expectancy of LEDs, I might still need replacement one day.

Bulb Quantity Use
T5 standalone
  • 20 green
  • 20 red
  • 20 yellow (white)
  • 5 blue

instrument panel (9 G, 6 Y, 1 B, 3 W), warning lights (10 R, 8 Y), radio flap (G), ashtray flap (G), suspension switch (G)

T5 double-sided
  • 10 white
  • 10 green
ashtrays (2 W), cigar lighters (2 W), LH display (2 G), RH display (2 G), A/C panel (3 G cut), ignitions switch (1 W)
T10 360-deg
  • 5 white
map reading lamps (2)
T10 stubby
  • 10 white
rear seats (4)
T10 double-sided
  • 10 white
glovebox, boot, door sills (4)
BA9s 360-deg
  • 2 white
ceiling lamp
Festoon 36 mm
  • 4 white
sun visor (2)

How much really? Well, that's 69. And if you add the following section, the switches: 79 in total.

Windows switches

They have already been discussed in Switches with LEDs. However, handling all these ready-made bulbs made me thinking. Why not do the same and prepare a small PCB, just the right size to fit the switches, keeping the LEDs and their resistors neatly packed?

Apart from the neatness of the solution, it has real advantages over the original: twice as much LEDs, meaning brighter display.

This takes care of all the internal lights. But what about the outside? Well, not much. H1-H3-H7 are definitely out of question, not only the light output is still very much beyond expectations, their geometry is so much different from the old filament bulbs and the headlight projector geometry dependent on it, that the light pattern is completely wrong and, of course, it's therefore illegal.

But large manufacturers like OSRAM have already jumped the bandwagon with replacement P21W and similar bulbs, so I think the legal situation might change one day, with the bulbs gaining the necessary EU and similar approval logos and accepted for road use.

Reversing lights

There is one location where I still thought a bit of experimenting will be in order: the reversing lights. We all know that our reversing lights fell prey to the beautiful rear design of the XM. Housed in the plastic trim between the indicators, the coloring reduces the light output to a large extent. So, with the risk of needing to go back to old bulbs for the MOT temporarily, I chose these:

They look very serious, don't they? Not the usual dozens of LEDs all around. But those present are from Cree and previous buyers all praise the very high light output. It would be really good to be able to see where we back up to...