[hotspoons]

Taking inspiration from On Rails Engineering and Tim Whit (who maybe didn't finish his project), I wanted to do an LED tail light conversion for my 2005 Elise, but I didn't want to pay obscene amounts of money for the 2006 lights that tend to not be durable, and I am a fan of the look of the chip-on-board (COB) halo lights that have come to market over the last couple of years.

So lets start with a bill of materials:

• 
  
  2 x High output LED reverse lights (1 pack of 2, in 4300k white)
  2 x BA15S pigtail connectors (1 pack of 2)
  1 x BA15D pigtail connector (1 pack of 2, you'll have an extra one)
  

Total cost of materials is $168 shipped as of 6/4/2016.

Additionally, you will need a rotary tool (e.g. Dremmel) with a diamond cutoff wheel; a soldering iron; solder; electrical tape; friction tape; heat shrink wrap; silicone RTV glue; a scraper; an 8mm wrench or ratchet; packing tape; and a cutting/stripping tool for the wires. If you are a crimper kind of guy instead of a solderer, adjust the instructions accordingly.

Here is how sexy you will look afterwards:

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[hotspoons]

First, start by removing the tail lights from the car. You need to twist each bulb out of its socket in the light housing (there are two sockets on the outboard lights, three on the inboard lights). Then, using an 8mm wrench or ratchet, unbolt the top and bottom nut holding the stud in place. The light housings are likely stuck to the paint in the buckets; you may need some force to get them out, and paint may come off. Don't worry though, it will be covered up by the lights when you reinstall them.

After the lights are out, prepare yourself for 3 or 4 hours of arts and crafts with plastic shreds going everywhere. Getting the lens separated from the housing took me a full hour on my first attempt, and I got the process down to 15 minutes by my fourth attempt.

The first step is to cut out the black glue that holds the lenses to the housings. I did this using a rotary tool with a diamond cutoff wheel. Basically, go deep enough until you hit real resistance, then you know you bottomed out the glue. Now using that depth, go around the entire circumference.

After the glue is cut out, there will be a touch more that you can't get to on the vertical portion of the housing/lens junction. You need to take a prying instrument (I used a flat bladed scraper) to pry the plastic lens off of the housing, do it every 1/2" all the way around the circumference.

Soon, you will be able to get a side pried up a bit; once this happens, go to the other side and try to pry that up. Keep going until you can finally lift the lens off of the housing.

Next, you need to cut the clear plastic diffuser disk out of the light housing. Using your rotary tool, cut from the center out at an angle all the way around the circumference, being careful not to knick the lens when you cut through the diffuser. This will not free it, but is necessary for the next cut, which will be from the outside angled inward. After you complete this cut, the disk should be free.

Now you have a mess! And a red lens, a chrome housing, a conical light shield for the reverse lamp, and a clear diffuser disk with a jagged center hole. Not to worry though, we will clean things up and hide the ugly bits later. At this point, the conical light shield and the clear or yellow glass lens for it can be archived or thrown away as these will not be used in upgraded lights.

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[hotspoons]

Next, clean up the jaggies on both the lens and the diffuser disk where you cut the two apart. It doesn't need to be perfect since it will be hidden, but you want it not to cause any clearance issues with the trim that goes on it later. You may also want to use a scraper and try to get as much of the black glue off of the housing and lens as you can. I used a sanding drum on my rotary tool:

Now you need to cut a notch into the diffuser disks for the resistors and wires to go through. I traced around where I could see the wires would come through; cut; tried to fit it; and repeated a few times until I got the notch just large enough to let the wires and resistors through, but not any larger. Once you have the cut sized correctly, do it for the other 3 disks. I also made sure that they were all lined up radially when I traced the template of the cut to each other disk:

Now that the diffuser disks are cleaned up, trimmed, and notched, the next step is to paint them with chrome paint. This is because they will be behind your light source, and every tail light I have ever peered into has chrome colored material behind the lights. So, sand the side you want to paint (I did the smoother side) with 200 grit paper; then clean them with rubbing alcohol; put them in a painting vessel; and paint them. I did 3 or 4 light coats, taking about 10 minutes between each coat:

Let them dry overnight.

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[hotspoons]

The next step will be to attach the LED rings to the diffuser disks. I did this using clear silicone RTV glue that is easyish to remove if you ever need to service these in the future, but it will still hold things put.

Now you will need to put some weight on the LED rings to make sure they don't want to come up from the diffuser disks. I used some of my wife's literature:

Let that sit for an hour or two, now you should have 4 integral lighting units:

The next thing to do is hide the ugly edge on the inside of the diffuser disks. While normally reserved for use on '94 honda accords with 22" rims from pep boys and stick-on fake hood scoops, go ahead and use the hoopty-style chrome trim you bought from amazon. Cut it into lengths as so (you'll need to figure out the length as I forgot to measure, sorry!), and angle the ends as shown so the ends will be parallel once wrapped around the inside of the disk:

Now, starting at the point that will be the bottom-most part of the light, apply the trim to the inside of the diffuser disk to hide the ugly. You will need to cut a notch exactly half way around, then leave a small gap between the end and the start. This is so the disk will lie flat on the housing, which has two ribs that go vertically.

And from the front; you can see the ribs in the housing below the diffuser disk:

All 4:

The next step will be to glue the diffuser disks to the housings. Run a bead of glue around the circumference, between the diffuser disk and the housing. Make sure you run the wires out of the back of the side hole on the housing. Let it sit for an hour, then run a bead of glue around the bottom of the housing, where you cut out the black glue at the beginning of this process:

Now put the lenses onto the housings, pressing them into the glue. Use some packing tape to hold the lenses tight to the housings as the glue sets:

And let them dry for an hour.

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[hotspoons]

The next step will be to wire the LEDs to the automotive connector pigtails. I did the outer ring red/black to connector red/black, then the inner two rings red/black to yellow/grey. This makes two separate lights you can manage later. Exact steps are: expose wires; twist them; solder them; heat shrink wrap them; wrap the loom with electrical tape; and finally wrapping the loom with friction tape:

Now is a good time to bench test everything. A 9 volt battery works fine:

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[hotspoons]

Now we can install the lights into the car. Go ahead and put them in the way you removed them, and secure them with 2 8mm nuts. Notice they look a little different now:

Next up is making the harness. What you need to do is make 4 circuits; one is a distinct ground and hot from the blue wire on the BA15D pigtail to the V-/V+ on the PWM dimmer; the output +/- gets run to the red and black connectors (outside LEDs) on all 4 connectors. The other 3 circuits share a ground, you can pull the ground from one of the two BA15S connectors.

How this gets connected to the car is that the driver's side brake light/tail light combo connector (one with the BA15D connector that is not the turn indicator) gets connected to the BA15D pigtail, which is wired to the two inboard brake lights, and all 4 outer rings for tail lights. Again on the driver's side, the turn indicator connector (BA15S) gets connected to a BA15S pigtail, which runs the outboard driver's side turn light. On the passenger's side, there is a BA15S connector for the passenger's side turn indicator - this is connected to the other BA15S pigtail, which is connected to a length of wire fed back to the driver's side, which is hooked to the outboard turn light on the passenger's side.

The short side (driver's side) of the harness will need a BA15S connector to connect to the outboard light's yellow/grey line. The long side (passenger's side) will need the harness to go from the other BA15S connector to the pass. side outboard light. These are for the turn signals. The hot red from the BA15D connector gets run to the yellow/grey line for the two inboard light connectors (for brake lights).

To make the harness, expose, twist, solder, and heat shrink wrap the connections:

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[hotspoons]

Now wrap the wires with electrical tape then friction tape to complete building the harness:

We will begin hooking everything up. Go ahead and replace the reverse bulbs with the BA9S/H21W LEDs you bought earlier:

And using cable keepers or some other means, run the harness along the back side of the trunk of your car:

Install the PWM dimmer into the harness where you wired in the connector, and use double sided foam tape to make it stay put:

Finally, plug the two BA15S headers into the sockets for the left and right turn signals, and the BA15D header into the socket for the driver's side brake and tail lamp. Pull the old incandescent bulbs out of the remaining light sockets; put some electrical tape in the unused sockets to prevent anything from contacting the hot side which is at the bottom of the socket; and tuck them out of the way.

And you are done! Well, you will need to address the hyperflash with a turn signal relay designed for LEDs.

 

[lobuzz311]

Awesome diy! Did you do this to the lights on your car or buy a backup set to work on? If backup, do you have a good source for them?

 

[hotspoons]

Awesome diy! Did you do this to the lights on your car or buy a backup set to work on? If backup, do you have a good source for them?

Thanks! I did them to the original tail lights on my car. Lots of guys have done the 2006 light upgrades on the 2005s, so you can probably post a WTB ad and pick up a set if you don't want to do this on your original lights.

 

[ZeRoSL]

Well done! Love DIY

 

[HiRez]

Very nice.
Although I already have the OEM Leds these actually look nicer! Wonder if it would be possible to have the turn signal in orange as is the standard in Europe.
Also I would need a rear fog light support which i am not sure you need in the US.

It's kind of a waste to cannibalise my 2006 lights but maybe i should have a look at buying some 2005 lights and find someone to help me.

Pretty sure you could make some $$$ selling these as plug and play somehow fully assembled. I would probably send you money ;-)

 

[hotspoons]

Well done! Love DIY

Thanks!

Very nice.
Although I already have the OEM Leds these actually look nicer! Wonder if it would be possible to have the turn signal in orange as is the standard in Europe.
Also I would need a rear fog light support which i am not sure you need in the US.

It's kind of a waste to cannibalise my 2006 lights but maybe i should have a look at buying some 2005 lights and find someone to help me.

Pretty sure you could make some $$$ selling these as plug and play somehow fully assembled. I would probably send you money ;-)

Thank you! Yes, you can get the COB rings in amber too .

The 2006 lights are constructed differently, so I don't think much of the fabrication part of this guide would apply. But I'm sure there are plenty of people with the 2005 lights (I think Ferrari 355 and 360 lights are almost the same as well) that have upgraded to the '06 lights that would part ways with them .

This really isn't that skilled of labor to do, I am usually a sloppy brute when it comes to detail work and I managed to make these turn out okay. It is just time consuming!

I did some back of the napkin math on all of the time I spent making my lights (after I addressed all initial inefficiencies), and I figured out that it would take me at least 5 hours to make a set of 4 of these. So I wouldn't necessarily be able to sell these at a price point people would pay for them

 

[jvbrugger]

Where is the dimmer set? Can you tell me more about why the dimmer is needed? Seems like you could either run them at full voltage/brightness, or you could put a resistor pack in line and eliminate the need for the dimmer??

A very cool project, tho'. Well done!!

 

[hotspoons]

Where is the dimmer set? Can you tell me more about why the dimmer is needed? Seems like you could either run them at full voltage/brightness, or you could put a resistor pack in line and eliminate the need for the dimmer??

A very cool project, tho'. Well done!!

Thank you! The dimmer (this one specifically) is placed here in the trunk:

The reason is that the rings are quite bright, and you may give the impression that you are riding your brake constantly at night if the rings are not attenuated to a lower output. If you follow behind any car at night time, you will notice that the tail lights are much lower output than the brakes and turn indicators.

The dimmers are just on the outer set of rings; the inner two set of rings run full brightness since they need to be visible during the day for brakes and turn indicators.

The reason for the dimmer is that it uses pulse-width modulation to lower the light output as opposed to increasing resistance/ lowering voltage, which may (?) be better for the life expectancy of these lights. OEMs use PWM to underdrive LEDs too (you can always tell in Chris Harris videos where the LEDs are flickering in slow motion). Plus I wasn't sure how much I wanted to attenuate the light output You can build a much more compact PWM attenuator out of a 555 IC, which I will probably do eventually.

 

[HiRez]

Thanks!


I did some back of the napkin math on all of the time I spent making my lights (after I addressed all initial inefficiencies), and I figured out that it would take me at least 5 hours to make a set of 4 of these. So I wouldn't necessarily be able to sell these at a price point people would pay for them

Never underestimate people with 2 left hands or lazy people ;-)

But cost of materials 168 + 5 hrs @ 20/hr = 268 + cost of a set of 2005 lights would be acceptable ?
I might just get back to you ;-)

But I will study your post with someone who is a bit handier than I am to see what I could do.

But again... compliments on your work. Looks good perhaps just a bit bright but the dimmer should be able to take care of that right?

 

[hotspoons]

Never underestimate people with 2 left hands or lazy people ;-)

But cost of materials 168 + 5 hrs @ 20/hr = 268 + cost of a set of 2005 lights would be acceptable ?
I might just get back to you ;-)

But I will study your post with someone who is a bit handier than I am to see what I could do.

But again... compliments on your work. Looks good perhaps just a bit bright but the dimmer should be able to take care of that right?

Haha yes, nice hourly rate . The rings are properly bright in person, it is just that cameras in general are going to pull up brightness in the dark so you get the illusion of them being super bright; they are adjustable regardless.

 

[jvbrugger]

"The dimmers are just on the outer set of rings; the inner two set of rings run full brightness since they need to be visible during the day for brakes and turn indicators."

Ahhhh, I didn't catch that on the installation thread. I completely understand the dimmer's purpose now. It differentiates the brake/turn brightness from the running lights.

Thanks!

 

[TedR]

Great DIY and write up. I suspect there will be quite a few that give this a try.

For those that want LEDs, don't want to DIY, and don't want to pay the price for 2006+ lights, I noticed that Elise Parts will be selling replacement LED units for our federal S2 cars for about $500, plus shipping.

https://www.eliseparts.com/products/show/53/1193/led-rear-lamps-s2/

 

[lobuzz311]

500 isn't a terrible price for OEM led tails, but the ones in this diy just look cooler / more modern. What to do, what to do...

 

[Skwerl]

You magnificent bastard! These look fantastic- far nicer than the new style tail lights I have. I installed these rings in my headlights. They look great there as well.

Josh