LED conversion -- highs, lows, and relay swapping
 

There's not all that compelling a set of reasons to switch to LED bulbs for any part of the 911 except the dash, in my opinion. There's a slight safety argument for the faster brake light response, I guess. But the problems with the directional nature of most LED bulbs means you're sometimes trading the safety of the fast response time for the danger of less-visible brake lights.

In my case, there was another factor. I wanted to cut weight to the back of the car, and I found a way to put together an LED setup that was lighter than my 911R-style lightweight tail lights. This also let me change the look of the rear of my car back to something closer to stock.

Before:

http://imagizer.imageshack.us/a/img534/1287/zmj8.jpg

After:

http://imagizer.imageshack.us/a/img42/2866/0rm2.jpg

But the trick to saving weight back there doesn't have anything to do with the bulbs you run, it's that big heavy 4+-lb box that protects the bulbs from the weather. My solution to that was to get an LED setup made for a submersible boat trailer, which allowed me to put together a very light box without having to be concerned with water intrusion.

Heavy:

http://imageshack.com/a/img823/5330/z2pp.jpg

Light:

http://imageshack.com/a/img59/8283/cxm9.jpg

Here's the inside:

http://imageshack.com/a/img836/3326/pz9n.jpg

As an added bonus, the multiple array of bulbs in the trailer setup eliminated the normal problem with LED bulbs, in that there are so many sources of light that you don't suffer from the directional issue.

Okay, all good so far, right?

Well, no. The problem with going to LED turn indicators is that you have to switch to an electronic flasher relay (made for LEDs) and have LED bulbs in front as well as in back. With no LED bulbs on hand for the front, I had to go with a very inelegant solution -- I soldered together a pair of incandescent replacements to piggy-back on top of the LED bulbs for the turn indicators, which I disabled.

http://imageshack.com/a/img835/7056/6aeo.jpg

So I was running incandescents all around for turn signals, but LEDs for running and brake lights in the back.

After a couple of weeks, the flasher relay and bulbs arrived. The first thing I did was to test the new bulbs in front. The seller promised a warm white bulb that would alternate with an amber front turn flasher.

http://imageshack.com/a/img836/1029/gadcs.jpg

As a reference, here's the incandescent front bulb:

http://imageshack.com/a/img845/5552/t4zc.jpg

So I ordered another set of LED bulbs -- this time with two arrays of amber light elements. They finally got here, but were significantly dimmer than the incandescents they were replacing. The camera doesn't show as much difference as there was in real life.

http://imageshack.com/a/img834/5707/i1ak.jpg

Still, they worked well enough that I thought I could finall drop in the electronic flasher relay and solder up the rear LED indicator lights.

Am I the only one who has the gas vapor cannister basically sitting on the flasher relay up under the dash? It clearly calls for a small monkey with long arms to make the switch, and there was a lot of German cursing done before I finally got the new relay in place.

Then I soldered in the LED sets and tested it out.

Crap.

Good grounds all around. Pretty fresh contacts for all the bulb connections. But suddenly I was getting the left rear indicator flashing at half strength when the right indicator was turned on and flashing. And the reverse was also true -- whichever side was not being signaled would blink along at half strength, but only in back.

I checked my grounds again, confirmed my wiring. Scratched my head. Cursed some more.

Couldn't figure it out.

So after cooling down a little, I decided to go back to incandescents for turn indicator lights. It just wasn't a big enough deal to lose more time over. So the first thing was going to be the tough part -- switching back to the incandescent flasher relay. More cursing. Scuffed knuckles. But finally, I got it in.

Then I put the incandescents back in front, and decided -- before getting out the soldering iron again -- to turn on the signals and see what the 'fast flashing' condition was like.

I didn't get it.

With incandescents in front, and the LEDs in back, everything worked perfectly. The dash indicators worked. There was no half-bright condition anywhere. Worked with running lights on. Worked with brake lights on.

It just worked.

So, I've left it that way. Maybe someone can explain how the incandescent flasher is getting the correct resistance from only two incandescent bulbs. Or maybe someone can steer me straight if there's some hazard to running things this way. But outside of that, I'm going to stick with this new arrangement.

Here you can see how the array of bulbs widens the visibility of the rear lights.

http://imageshack.com/a/img835/9017/3b3f.jpg

Interesting Jack.
I'm in the middle of almost exactly same project as you are.

First to your question regarding the flashing circuit. You think you are onto something with the resistance. I have not seen the schematics for the flasher, but from what I too understand, it needs a certain resistance in the bulb(s) in order to work as intended.

Good to know that one bulb in front will do the trick.
You see, I too want to shed some weight. So I just cut out unwanted material from the original rear housings, and fitted new inside/ back wall with the help of epoxy fiber, polyester, and plastic back plate. :)
Now I am in the process of mounting some LED "sheets" on the back wall inside. The preliminary tests are looking promising.

Some pics to show what I mean:

First cut (Not pretty, but a few more precision cuts later not too bad)
http://i132.photobucket.com/albums/q...ps44778c06.jpg

LED sheet:
http://i132.photobucket.com/albums/q...ps05c0eb9d.jpg

Jack,

I'm curious about this as well. I added the Hella LED TBL for added visibility and it is well worth it, but that is just augmenting the incandescents. I have a friend who did the LED conversion on his Datsun 260Z and he had a similar problem with the resistance. In my opinion, he also lost some visibility in the bright sun. The LEDs tend to work well at night but in the daytime they can be less visible. I think this is because of the directionality and you gets less reflected light from inside the housing. Still, you've got quite an array of LEDs there!

As far as the flasher relay... The way I understand it, when you switch to LEDs there is a minimum load that is required for the turn signal relay to work. If you go with all LEDs, the lower load isn't enough to trigger the relay, so that's why you need one designed to work with LEDs. By just replacing some of the incandescent bulbs instead of all of them you probably have enough load still to trigger the relay. I think a concern might be that if an incandescent bulb failed, would you lose all your turn signal function? Or if you replace an incandescent in the future with a more efficient bulb, might you fall below the threshold where the relay won't work?

My suggestion is to figure out a way to use vintage lenses or the ones you had. The new lenses don't fit the look of your beautiful 911.

Jack, a lot of the aftermarket trailer lighting systems are designed to 'expect' that the tow car isn't set up for them. In the circuitry you probably find that the manufacturer has included a resistor to make the flasher think its flashing incandecent bulbs... When you combine the resistor in the light array and the LED specific flasher, perhaps there too much resistance leading to "inconsistencies" such as dimness?

I personally like the more stock looking lights on your car... As you know, I had the 911R lights for a while too, but they do seem a little odd on a fat RSR rear ;)

That's cool, I've been putting together a list of parts to do a similar thing. But for me I want more quality light is the reason. New lenses might be all I need.

Jack,

a flasher relay requires a certain minimum amount of current to be drawn to work properly. Modern LED are not nearly drawing as much current as an incandescent light bulbs. In the old days a flasher relay was a bi-metal strip with some wire wound around it acting as a switch: When the lights came on the wire would heat up and the strip bent. the circuit opens, the strip cools and bents back to closes the contact. If one of the two flasher bulbs was out the frequency nearly doubled and the working flasher light goes very fast......

That is why others suggest to add a beefy resistor in parallel with the LED. Try something like a 100 Ohm and make sure the resistor is able to handle the current. Maybe start with a 2 Watt version and see if it can take the heat. The math is (14.4/100)*14.4 = 1.96 Watt. Since the duty cycle is about 50% the resistor will dissipate about 1 Watt.

Ingo

Otto, that's a cool project. I've been thinking about doing something like that with the front buckets. They've gotten so expensive though, that I'm a little cautious about cutting a set up.

Maybe another aluminum box for me?

John, I think you're correct about why the LED lights are working with the old-style flasher -- and why they didn't work with the LED (electronic) flasher. Each LED is paired with a resistor on the board. In this picture, you can see how the whole board is sealed in clear plastic to keep water out.

The part that doesn't makes sense about including the resistance is that a car or truck using the trailer is still using all of its existing bulbs, whether they're incandescent or LED. This would make me think you wouldn't need to worry about adding resistors, since if the car has an electronic flasher relay and LED bulbs, the resistance might cause problems for it.

http://imageshack.com/a/img838/5113/p1j1o.jpg

Here's an actual 2.8 RSR:

http://m8.i.pbase.com/g4/53/615153/2...8.iktQGWgL.jpg

It's interesting that they got this model down to 1852 pounds, and didn't switch to the 911R tail lights. Maybe they made lightweight boxes for them?

Hi Jack,
have you taken a look at this website: https://www.superbrightleds.com/carbulb_notes.php

Under the section Turn signal issues with LED bulbs, they say:

LED brake/tail lamps will not flash with thermal flasher units due to their extremely low current draw. [...]
Another fix is the installation of Load Resistors which are wired across (in parallel with) the turn signal bulbs to simulate the load of a standard filament bulb.

I'm not an electrical expert, so if you find a fix, please do let us know. I am interested.

There's some confusion in the replies (which is fair enough, as the original post is LONG). There is no problem with the LED assemblies working with the conventional flasher relay. They come with the resistors installed.

What surprised me was that they would not work with an LED-specific electronic flasher relay. But that it probably because of the resistors, too.

Don't these guys have a lite weight tail assembly (tech9.ms) for sale? See post #123. Probably $$$s...

edit for link

http://www.impactbumpers.com/forum/index.php?/topic/17319-birth-of-a-rally-car-tech9-ruf-scr/page-7

Yeah, there are a few different products available out there. I don't think any one of them approaches my cost, which was $38 for the LED stuff and $0 for the scrap aluminum.

And for what it's worth: Tech9 claims to save 5.5 pounds from stock, while mine saves 6.4 pounds.

I made my own

http://forums.pelicanparts.com/uploa...1314583519.jpg

http://forums.pelicanparts.com/uploa...1315359284.jpg

http://forums.pelicanparts.com/uploa...1315359339.jpg

http://forums.pelicanparts.com/uploa...1315850227.jpg

https://www.youtube.com/watch?v=nrMjNak28jE



The only reason the yellow is different is because I used clear on the flashers and amber on the marker lights.

http://forums.pelicanparts.com/uploa...1316830749.jpg

Similar concept though.

I got the square lights from superbrightleds and the round marker lights are from a trailer mfg company - they are 1" marker lights all LED's

That looks great, Jeremy. I wish I knew fiberglass.

I've got one last postscript on this -- a final little tweak with only a small weight hit.

Who knows why, but most of the rear lens has an etched pattern to refract the light. But on the forward section, the plastic is clear.

http://imageshack.com/a/img835/6904/xcav.jpg

To fix this, the factory boxes include a lens piece. It weighs an ounce.

http://imageshack.com/a/img841/5935/9ipfh.jpg

For six bucks, you can get a clear piece of refracting plastic that they use in suspended ceilings. You can cut it with ordinary scissors.

http://imageshack.com/a/img834/7340/5kopq.jpg

And it weighs very little. Not even enough to register on my scale.

http://imageshack.com/a/img845/8703/bmz0.jpg

Same function:

http://imageshack.com/a/img845/4424/dlht.jpg

Here are the naked running light bulbs:

http://imageshack.com/a/img845/7786/t17s.jpg

Refracted:

http://imageshack.com/a/img838/7607/r69d.jpg

And covered with the lens:

http://imageshack.com/a/img843/6310/9je7.jpg

I like that solution - very elegant

The LEDS I have on the back of my early 911 are quite bright they are big rig clearance lights that fit the 911R signal housing... and a adding a resistor to the turn signals allows the turn signals to work as expected. As always chasing a few ounces at the extrema of the car is an interesting exercise.

http://forums.pelicanparts.com/uploa...1398908762.jpg


My car weighs 1846# wet :p



http://forums.pelicanparts.com/uploa...1398909017.jpg

Having done a lot to cut weight... the cars that are 500 pounds lighter just boggle my mind.

I bought the solid state flasher, took it apart and replaced the nichrome wire current flow sensing "resistor" with one higher enough in value to drop enough voltage with the lower LED current flow.

It bobbles my mind the effort you guys make to shave a pound or ounces. More power to you, just an observation.

Reminds me years ago I through- hiked the AT trail and what some guys did for weight savings, like drilling holes in forks and toothbrushes when I was carrying beer and cookies...., but I guess it all adds up. :D

i'm going to attempt this soon, probably using led truck lights in a box like jack's. would you guys that have done the led conversion do it again? any words of advice before i go down this road (haha) and start ordering parts?

thanks.

I have been doing some work on electronic LED compatible flashers for the 911. In my 1973 the stock flasher is a 4 pin and I did convert it for use with a 3 pin LED flasher.

CLICKCLACKBOOM started this thread and I took his suggestions and they work.

Quick summary is that the 4 pin has an extra set of flasher contacts that really not necessary at all. As a matter of fact the Porsche wiring is a bit puzzling and unnecessary complicated.

http://forums.pelicanparts.com/porsche-911-technical-forum/779096-led-conversion.html

the 3 pin conversion is easy and then you can get an LED compatible 3 pin flasher. Mine even has a variable flash control.

Hey Jack, hope you're well?

It'd be a big piece, but with the ever reducing cost of 3D printing rigs, it may be worth investigating?...nice n light

Talking of weight saving, if you've not seen it already, Roland (proffighter) is engineering some fantastic lightweight pieces on his 930 project --->

Another Rust Combat

Cheers
Spencer

Just a FYI

Rothsport has these available now

Welcome to Rothsport Racing - Products

http://www.rothsport.com/Products/Ce...es-1-Large.jpg

Wow I have been waiting for those and then....$500.....argh cannot justify. Going to have to make my own.

Here is the front impact bumper car marker light converted.
http://forums.pelicanparts.com/uploa...1413848752.jpg
http://forums.pelicanparts.com/uploa...1413848763.jpg
http://forums.pelicanparts.com/uploa...1413848785.jpg
http://forums.pelicanparts.com/uploa...1413848796.jpg

I installed iroc bumpers and had to loose one light and wanted to upgrade. This was way too simple to do. Took 10 minutes and looks great in use. I used some leds I got on ebay, the block with two I use for the marker lights and the two little round ones are brighter and use them for the signal. With the reflector inside it works great.
I already had the flasher upgrade so that was not an issue for mew.

What were the LED "pucks" listed as on ebay.

The round ones are eagle eye drl lights. In 4 and 10w sizes. The block one is just a drl day time running light. Can't remember much about that one. I've had them for a while.
If I were to do it again I'dahe sure the blinkers were more level because the markers flip flop side to side. Looks odd.

<iframe width="640" height="480" src="//www.youtube.com/embed/oTqHVxHf8Zo" frameborder="0" allowfullscreen></iframe>

I finally finished the DIY of the lightweight rear LED lights. Thought I'd upload some pics.
Worked out well, even though the LED pads are E-bay cheap-stuff. No issues with turn signal blinker, probably because the front is untouched.

Some pics:

Ready on the bench.
http://i132.photobucket.com/albums/q...psm4azsky9.jpg

Installed and testing without lense.
http://i132.photobucket.com/albums/q...psjz4yatxv.jpg

Testing with lense on, a little strong driving light.
http://i132.photobucket.com/albums/q...psyzyadwhi.jpg

And finally a shot with indicator on.
http://i132.photobucket.com/albums/q...ps1u3ub0zf.jpg

After these pictures werre taken I adsjusted the strength down a little bit for the driving lights, and it was spot on. Notice that I have two LED pads working together for both driving lights and for brake light. The intensity for brake light is about the stock brightness. I kept the indicators as strong as they seem there. After all they are difficult to see from odd angles, wich is likely for those lights.

I don't really know how to start this reply so I'll dive straight in. I think you are all playing a dangerous game swapping in cheap led panels into your light units! LEDs have many characteristics that need to be accounted for in the design of the drive circuitry.

Simply plugging them in and seeing that they light up doesn't even come close to assessing suitability for road use. Electronic engineers (like me) spend hundreds of hours designing circuits to tame the heat, voltage variations, damp, vibration and other 'variables' that the environment throws at our creations before we even get close to a prototype. We then undertake extensive and exhaustive testing of our prototypes and then have to meet many approvals before we can launch a product. There are very good reasons we do this, safety being number one, durability a close second.

Put it this way, if I gave you a set of unknown wheel nuts that fitted your car would you be comfortable with taking it for a high speed run? You'd probably want to know the material, how many threads it has etc. If they look ok, they must be ok right? What if I then said they were off my wheelbarrow?

I worry that your homemade lights will 'work' in the garage and be given the ok. Then during a cold winter or indeed a hot summer, or when a solder joint fails due to vibration, or damp enters the circuit, or when the battery is slightly flat or the voltage regulator spikes your LEDs will fail and you will be rear ended. The person who hit you will claim no tail lights and the assessor will find your non approved creations. A bit dramatic perhaps but you get my point.

Not trying to poop on this thread but be safe people!

Here is the simplest article I could find to give you an insight on the technical challenges of driving LEDs properly:

http://www.ledsmagazine.com/articles/print/volume-4/issue-8/features/driving-led-lamps-some-simple-design-guidelines.html

Are those builds legal in US?

For what it's worth I use the plastic part below that is both light and has held up on the track for years.

Indicator Unit Housing Rear (Plastic). Porsche 911 1970-89 (OE Ref: 91163193900, 91163194000) - 9116319 | Design 911

I have them too, not in use yet, but here (scoll down) some details about:

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/634616-another-rust-combat-3.html

No, not really. We just have nobody inspecting the cars, or policing the rules.

JR

Thanks for bringing that up!

It is true that you should always use caution when doing any modification to your car. I would never attempt to to anything like this if I didn't know electronics like I do. I probably wouldn't even come to think of the idea even. But since electronics is my profession I have no problems doing this mod. And this is no rocket sience. By the way, the LED pads I use do not require any driver. It is just a grid of LEDS on a board with a resistor in series to control the voltage/current. That's the way I am able to "dim" them too, by use of an external resistor.
I think that doing work on the brakes myself is more "scary", although this is completely legal and in the realm of any home mechanic. The consequences are huge if anything is not right with the installment.

So be safe, -absolutely. Make sure you test properly and that you know what you are doing. And in this case, make sure that you keep an eye on that the lights in fact are working regularly, like you should do anyway. Remember; a normal bulb is'nt exactly bulletproof either.

And while I'm not an engineer of any kind, I used a manufactured (and approved for road use) set of lights that were designed for universal 12V applications and a boat trailer. In terms of weather-proof-ness, they're designed to be submerged in saltwater.

But I would agree that caution is in order for any modification that an owner is doing that could decrease safety.

Jack, it's the ebay specials that are more of a concern. IMO, they are no more fit for purpose than Christmas tree lights.

Ok. So I may have a thing about LEDs, here's why....

My company developed the multi colour cabin lighting for the Airbus A380 super jumbo where we learnt that LEDs are not just 'little lights'. It is an extreme example but thought I'd share to give you an insight. Maintaining a controlled light output required a hybrid constant current / PWM drive circuit. The requirement is that the lights should maintain the same output level for 30 years. This also meant that brand new replacement units can be placed alongside potentially 30 year old units and be exactly the same colour and intensity. We worked with the LED manufacturers to derive the predicted fade profile for 30 years. This profile is different for different colours (we were using red, green, blue and amber). A microprocessor records the instaneous drive current dependent on intensity and colour demanded along with the elapsed time that each led had been run for. This is used along with measured temperature to correct the drive intensity according to the fade profile. Essentially, new units are underdriven and old units are overdriven to give the same output. Each unit is setup and calibrated using a colour light meter and conforms with the standard CIE colour gamut chart. The project took 5 engineers 18 months to complete.

If you've seen the sunrise / sunset cabin effect on the plane, that's the result of a lot of hard graft!

Saw it a few months back - it's impressive Jonny.