LED Update and Question
 

I have recently become obsessed with replacing all of the bulbs in my 911 with some sort of LED replacement. I think it's because I feel like 'modernizing' everything about the car but the looks, if that makes sense.

First, I installed LED gauge lights by a forum member named rothaus that made an incredible difference. (a tutorial on how I did it is at http://forums.pelicanparts.com/porsche-911-technical-forum/809742-led-gauge-tutorial.html)

Next, I replaced all the interior lights with EBay LED bulbs and installed under dash lighting (see http://forums.pelicanparts.com/porsche-911-technical-forum/888192-new-interior-lights.html)

Then, I bought spoke's LED brake lights, which made an incredible difference and will probably decrease the likelihood that I'll be rear-ended by a text-messaging soccer mom with 5 kids in her van.

Today, I replaced the reverse lights with these bulbs I got on EBay:

http://forums.pelicanparts.com/uploa...1449875402.jpg

And the result is pretty dramatic:

http://forums.pelicanparts.com/uploa...1449875507.jpg

So, here's the question:
I tried installing LEDs for the turn signal bulbs, but when I did, they began flashing at double-speed like they do if you remove the bulb completely. The lights worked and were nice and bright, but they blinked way too fast. I'm sure it has something to do with a voltage drop or something.

Is there a way around this so I can still use LED bulbs?

I should add that in the picture, the new reverse light is only installed on the right side for comparison.

There is a solid state flasher EP 36, that will work with LED's or incandescent, I got mine from Amazon:
http://www.amazon.com/gp/product/B00064LQLC?psc=1&redirect=true&ref_=oh_aui_search_ detailpage
You will need to ground the common wire connecting the indicator bulbs in the tachometer, on mine it is blue/white.
Search the LED Brae lights thread. You will find this and other info, including the effect on the cruise control
Good luck,
Dave

I have just put in Spoke's backlights/brake lights- really good!
I have tried to instll some LED replacement reversing lights but not a good fit- can you send me the ebay link for yours?
Thanks
Clive

Sure, it turns out those were from Amazon. Here you go:

http://www.amazon.com/gp/product/B00OGXID7E?psc=1&redirect=true&ref_=oh_aui_detailp age_o03_s00

Also, I forgot to mention that the seating little pins were offset on the LEDs but were even on the original bulbs, so they wouldn't go in easily. I took a Dremel tool and ground down the uppermost pin a little and then they fit fine.

Phillips makes a replacement bulb for the directioanals that doe not require a flasher replacement.

RSTarga, you don't happen to know a part number or link for it do you?

Peter,

Hyperflashing is a safety feature built into most car's flasher relay. The flasher is designed to flash at 2x rate (hyperflash) when the loading is less than the wattage of 2 normal bulbs. Normal bulb is about 20W. So 2 bulbs burn about 40W.

If the flasher senses something like 30W or less, it will hyperflash to alert the driver that a bulb is burned out. LED replacements burn much much less, maybe 3W to less than 10W. To replace front or rear or both with LEDs requires a change to an LED-compatible flasher.

As Dave mentioned, the EP36 is LED-compatible and plug-in compatible with the 911 standard flasher. Every FLAPS that I've checked (Pep Boys, Autozone, Advance Auto, etc.) carry EP36 on the shelf for around $15.

Thanks spoke! I figured the voltage difference was the issue. I'll definitely try the EP36. I'm assuming that would be needed with your turn signal LEDs anyway, right?

Yes, my turnsignal boards burn about 5W each. When I did the first one, I realized I needed an EP36. Really annoying when turnsignals hyperflash. I've seen this a lot in work trucks when turnsignals are replaced with LED types.

The flasher is behind the dash. I found mine by going through the front trunk. It helps to have the turnsignals or 4-ways on and just follow the clicking sound. Replacement took about 1 minute.

What you meant...

;)

Might be easiest to replace the flasher by reaching through a gauge hole.

Ahh, sorry. That makes sense--I guess it's 12 volts all the time, isn't it.

My electrical experience is limited to the Alabama multimeter--if you touch a 9 volt battery to your tongue and it tingles, it's probably good, if you touch a lawnmower spark plug while it's running and your arm shakes, it's running fine, and if you touch a household wire and piss your pants, then it's a 110 line.

And if you go #2 its 220v?

What was was really, REALLY meant... :p

http://forums.pelicanparts.com/support/smileys/wat5.gif

Well, see, the wattage determines the amperage, given the voltage, divided by wwest's IQ, which is more math than I can do.

Maybe it's the impedance. Or the phase. Or the weight.

:p

The reason you had to "ground down the uppermost pin" is you used the wrong type of bulb. The bulb you listed is a replacement for an 1157 which is a 2 filament bulb.

The backup lights use an 1156 which is only a single filament bulb so it doesn't need to be "keyed" with offset pins.
Try this one from the same supplier: http://www.amazon.com/SiriusLED-Bright-Projection-Signal-Brightness/dp/B0105LW41G/ref=sr_1_1?ie=UTF8&qid=1449929648&sr=1-1

It is a 35W equivalent and you will need to click the options for 1156 and white.

This thread should help you with your problem:
http://forums.pelicanparts.com/porsche-911-technical-forum/287390-i-solved-led-indicator-problem.html

I bought an EP35 and an EP36 and neither work with my SC -- seems there's a missing fourth Common (C) pin.

I think I need an EP26 according to some other threads I've been reading, those are a bit harder to find.

What is not working? Pin 31 is ground. Pin 49 connects to 12V and Pin 49a goes to the lights. These 3 are all that is needed to flash the external lights. The K/C/C2 4th pin is usually used to do something with the dash indicators.

EP26 and EP36 are almost identical. Both are available at your FLAPS.

The EP26 that I've purchased from Autozone had the 4th C terminal but it did not connect to anything. I took it apart to verify.

In 914's I've seen the 4th terminal labeled as K, C, and C2. In some, K would connect to ground and C/C2 would connect to 12V when the lights are flashed.

here is what I used and I didn't have to replace my original flasher.
Amazon.com: Philips 1157 P21/5W Red X-tremeVision LED Exterior light (Pack of 2): Automotive

What happens with the EP35/36 is that the all flashers flash together, with no dash indicators, regardless of which direction I move the stalk. The side being flashed flashes brighter than the one that's along for the ride.

I put in an EP26 and got a no-flashers at all situation. Hazards work correctly with either setup. Wondering if there's not a problem in my switch or something. More troubleshooting tomorrow.

Here are 3 similar schematic diagrams for the turnsignals. The first two are from the manufacturer of the EP26 with 4 terminals and EP36 with 3 terminals. The third is a diagram I put together for the Porsche 914 with a 4 terminal flasher like EP26.

The important thing to note in all of them is the flasher is a single wire in (49) and single wire out (49a). The flasher has no idea whether all 4 signals are on or only 2 on one side. When it is presented with a load, it toggles on/off at about 1 second rate. That's it. It either flashes or not. It can't direct the current to either side. The hazard switch and turnsignal stalk switch does the routing.

The hazard switch or turnsignal stalk switch determines if both sides or one side flashes. The flasher has nothing to do with both sides flashing at once.

Here with EP36 the 3 bulbs shown on each side indicate front and rear bulbs and dash indicator. A link was posted a bit back in the thread of someone who had to rewire the dash indicators to work correctly.

http://forums.pelicanparts.com/uploa...1449978488.jpg

Here's EP26 showing the 4th terminal C2. Here C2 is connected to the hazard switch and is shown as an input and grounded when the hazard switch is active. I don't fully understand its use. The unit I tested the C2 terminal did nothing and wasn't connected to anything. There were footprints for components but they were empty.

http://forums.pelicanparts.com/uploa...1449978959.jpg

This is the schematic for '70-'73 Porsche 914 with a flasher with the 4th terminal labeled K. The K lead energizes the common wire of the dash indicators. If the 4th terminal is not present, normally both indicators will flash equally for L or R turnsignals. Again, it is this common lead which was detailed in the before mentioned link.

http://forums.pelicanparts.com/uploa...1449978217.jpg

Since you also replaced your brake lights, it would be a good idea to verify that the cruise control still functions as expected. Remember that the cruise module needs to be able to "see" the brakes being engaged in order to disengage cruise.

Good reminder.

The brake PCBs and 3rd brake PCBs that I am making are compatible with the CC input. If you replace all the bulbs with off-the-shelf LED replacements, chances are they do not have a ballast resistor as I've used and the CC may not operate or may disengage unexpectedly.

Each of my brake boards has enough resistance to be compatible with the 911 CC unit. So if one replaces the brake lights with off-the-shelf LED replacements and uses my 3rd brake light PCB, the CC unit will work.

I just mentioned that because it was top of mind. My cruise has never worked and I'm just getting around to figure out what's wrong. I borrowed a spare known good cruise module from Uwanna and it did not fix it. I have Phillips LED brake lights. I'm going to swap the LEDs for standard incandescent bulbs while I continue troubleshooting to rule out the LEDs being an issue.

I also bought two "1156-WHP28-T: Cool White" LEDs for the reverse lights. People don't pay attention to cars backing out of parking spaces much as it is and if you're in a small car sandwiched between two SUVs in a parking lot you can't see what's coming. It's more about making me visible to the other idiots out there.

Adding a 3rd brake light to the top of the rear window also helps to get a brake light more at eye level with a driver behind you with today's higher cars.

I also have a relay kit that I got from Daniel Stern that makes the fromt side marker lights blink in conjunction with the front turn signal indicators. With the headlights on they are normal function until the turn signal is activated, in which case they blink. With the headlights off they are off but blink with the front turn signal indicators. I haven't installed it yet but plan to one day.

I bought a set of the Phillips LED brake lights too. From measurements on 2 different 911's, it looks like the CC unit dumps about 7ma into the brake lights. With the Phillips LEDs, you should only see about 3V across the brake lights w/o the brake pressed. You should also be able to see the LEDs lit very gently w/o brake pressed and running lights off.

It would be prudent to put bulbs back in when testing the CC unit. After the CC unit is working, then put the LEDs back in. You always want only one variable in an equation.

To me the 3rd brake light is the most important brake light on the car. It is the only brake light which does not have other functions. The normal brake lights have a second function as running lights. On some cars the brake light is the running light and the turnsignal.

If you don't have a 3rd brake light, put one on.

All (spoke)

I did some testing today with different flashers. Changing the fronts to incandescent bulbs helped, but I didn't want to get into rewiring the dash indicators, so I went back to all four incandescent bulbs for the flashers.

The table below shows what results I got. The picture shows the bulbs and flashers (not stock flasher) that I was using.

Any thoughts/ideas on what was causing the double-flash behavior? It's really weird.

http://forums.pelicanparts.com/uploa...1450053841.png

http://forums.pelicanparts.com/uploa...1450053914.jpg

Nice data. This is way to do testing. It allowed me to get to that ah-ha moment.

Table 1. All external LED

Flasher
Stock: Won't even pull in; It's expecting 20-40W; Your load is about 10W; does not work.

EP26/36: EP26/36 does not connect anything to the C2 lead. Thus when you put the turnsignal on one side, the 2 indicators in series light and (without C2 grounding) powers the other side. You must ground the center connection of the dash indicators for this to go away.

4-way
Stock: 4 LED loads is enough to pull the relay and flash. I'm surprised it didn't hyperflash.

Dash indicator:
EP26/36: I expected both to flash. See the 914 schematic; the C2 connection is gone with EP26/36; You must ground the common connection of the dash indicators for proper operation.

Table 2: Front bulb, rear LED

Flasher:
Stock: It thinks one bulb is out and hyperflashes as a safety feature.

EP26/36: The exterior bulb is a very low impedance and keeps its associated LED from lighting up even though the 2 dash indicators are dumping current into the bulb+LED.


Bottom line is you must ground the common wire to the dash indicators. This is quite easy to do. Get a couple of spade connectors and crimp them on to a short wire to make a "Y".

One spade on each indicator and the other one to a ground on the tach. It's really easy with one of the pigtail connectors shown below. When I start selling turnsignals, I'll include one of these with the LEDs. This will go on the brown ground wire on the tach. I can send you one if you can't find one. I had to order a pack of 100 of these online.

http://forums.pelicanparts.com/uploa...1450056353.jpg

Thanks Spoke,

I have one of those pigtails so I can make a Y, will do here soon at some point. You're saying that if I ground the indicators, the LEDs will function properly. I just need to make a brown female-female-female Y, remove the blue/white common wires in the dash and replace them with the new Y spades, then join those to the existing ground on the tach?

Yes. It took me a while to realize that the 2 indicators in series were powering the other side. With the center grounded, the left and right sides are now totally isolated.

I even had this happen to a guy with his 914 and my turnsignals and I didn't recognize what those indicators were doing to the circuit.

Spoke, thinking about this some. To add to your diagnosis (interesting) - what do you think stopped the double-flash behavior when I put incandescents into the fronts? Still no ground at the indicators, but the flashing behavior was correct (though the indicators both flashed.)

It did seem with the LEDs that the signal not being selected was flashing with less intensity than the other; so could it be that the indicators are 'letting a little current through' to the other side; enough to power an LED+LED combo, but not to power an LED+incandescent? (hence why the flashing worked properly when an incandescent was introduced, but the indicators still both flash?)

That looks like what I used for my brake lights. Do you have cruise control? If so, have you tested that your cruise properly disengages when using these?

It's a 73, no cruise control, but I wouldn't use it even if I had it. Thats what planes and trains are for.

It's all about sharing a voltage when you have components in series. Example: Take 3 equal resistors in series across 12V. Each resistor will have the same current (I) and because their values are the same (R), each will drop 4V (I x R) for a total of 12V.

The higher resistance a resistor has when in series with other resistors, the more voltage is dropped across the higher value resistor (I x R).

Take the circuit below with turnsignal on the left side is ON. The LEFT turnsignal sees 12V to GND and is on brightly. The RIGHT turnsignal sees some of the 12V but shares the voltage with the L.IND and R.IND indicators.

If RIGHT is an LED, its resistance is high and much higher than the indicators so little voltage is dropped across the indicators and most voltage across the RIGHT LED and RIGHT LED lights up.

If the RIGHT is an LED in parallel with a very low resistance standard bulb, the total resistance of RIGHT is very low. Thus L.IND in series with R.IND indicator are much much greater resistance than RIGHT. So most voltage is across the indicators and almost zero voltage across RIGHT. Thus the RIGHT LED is off.

GND --- LEFT --- 12V --- L.IND --- R.IND --- RIGHT --- GND

If you ground the center connection of the indicators then you have this circuit:

GND --- LEFT --- 12V --- L.IND --- GND --- R.IND --- RIGHT --- GND

So with the left turnsignal on, LEFT see full 12V as before and now L.IND also sees full 12V. RIGHT bulbs and R.IND indicator see zero volts and do not light at all.

^^^fantastic explanation, thanks spoke!

Unfortunately, my cruise control module only serves to hold up my stereo wires, so I can't contribute any real data to whether the LED brake lights affected it at all. I'm hoping to fix the cruise at some point, but it is a little further down the list.

I have an EP36 on the way, so I will post back any results I have with it. I've got some piggyback spade connectors, so I'll try wiring it to the gauge ground that way.

LED Hyperflash
 

That's exactly the ones I tried and it caused the rapid flashing. I have an 86 3.2, so I don't know if the system is any different than your car, though. I'll be trying them again with a new flasher relay in a couple of days, tho

Besides the Spoke or Philips brake, blinker and running light boards / bulbs, does anyone have a source for quality LED interior & exterior (city lights, license plate) bulbs? A full kit would be pretty ideal (hint! hint!).

I'm not wild about randomly sourcing all of the different part numbers from fleaBay's GenPop if it can be avoided. I'd like to get replacements for as many bulbs as possible (including underhood and decklid units). I think the cigarette lighter bulb is the same as the gauge bulbs. Anywho, thanks for listening.

A full kit would be a great idea. I considered it, but I still have several bulbs to figure out--specifically, the little bulbs beside the turn signals (are those city lights)? Mine aren't labeled with anything that would help me figure out what bulb type it is.