Turn Signal Indicator Wiring Question / LED upgrade

[memotronics]

I had a customer that replaced the turn signal incandescent with LEDs in his 1968 912, and purchased an LED-Flasher to go with that. The issue that arose was that when he turned the stalk to the left or right, all 4 corners would flash.

I looked at the wiring diagram and determined that this was likely due to the incandescent indicator bulbs in the tachometer cross-feeding to the other side.

After looking at the diagram some more, I cannot quite understand the design decision, can someone enlighten me on the following:

The in-dash indicator bulb for the RIGHT side is wired to the LEFT front/rear turn bulbs. Vice versa, the in-dash indicator for LEFT is wired to the RIGHT front/rear bulbs. The "other ends" of the indicator bulbs are wired to the pilot-terminal of the flasher. If I interpret the intent correctly, this means that when I turn the stalk to the left, then the right-side turn signal bulbs are used as a ground for the indicator, and vice versa.

My question: Why didn't Porsche wire the left indicator to the left turn-signal bulbs and the right indicator to the right turn-signal bulbs, and just ground the turn-signal bulbs at the tacho? And not even bother feeding those indicator bulbs from the flasher ?

I have a feeling I'm missing something.

[Classic 911]

Following


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[Jonny H]

Originally Posted by memotronics

I had a customer that replaced the turn signal incandescent with LEDs in his 1968 912, and purchased an LED-Flasher to go with that. The issue that arose was that when he turned the stalk to the left or right, all 4 corners would flash.

I looked at the wiring diagram and determined that this was likely due to the incandescent indicator bulbs in the tachometer cross-feeding to the other side.

After looking at the diagram some more, I cannot quite understand the design decision, can someone enlighten me on the following:

The in-dash indicator bulb for the RIGHT side is wired to the LEFT front/rear turn bulbs. Vice versa, the in-dash indicator for LEFT is wired to the RIGHT front/rear bulbs. The "other ends" of the indicator bulbs are wired to the pilot-terminal of the flasher. If I interpret the intent correctly, this means that when I turn the stalk to the left, then the right-side turn signal bulbs are used as a ground for the indicator, and vice versa.

My question: Why didn't Porsche wire the left indicator to the left turn-signal bulbs and the right indicator to the right turn-signal bulbs, and just ground the turn-signal bulbs at the tacho? And not even bother feeding those indicator bulbs from the flasher ?

I have a feeling I'm missing something.

The way they have wired it means that the dash indicator will not flash if the turn signals are not working.

Informs the driver of a blown bulb or wiring fault perhaps. Pretty neat.

[spoke]

When changing to LED turnsignals for older 911s and all 914s, the issue you notice is common where one side turnsignals blink as do the other side to a lesser degree. I call this ghosting. Are both L and R indicators in the dash flashing together?

What LED compatible flasher relay was installed? EP26 is pin compatible with the 911/914 but not pin functional as C2 is not powered.

As you noticed the L and R indicators in the tach are wired together on one side and driven by the K/C2 pin of the flasher relay. The flasher relay had a dual use in early 911s and 914s to also flash if the ebrake was pulled or the brake master cylinder fault switch was tripped.

To allow the OEM flasher relay to flash normally (1 flash/sec) with the tiny brake warning light as a load, the OEM flasher would not hyperflash (2 flash/sec) if one of the turnsignal bulbs burned out like most older vehicles would.

Without hyperflash to warn the driver of a burned out turnsignal, Porsche decided to use the L and R indicators to warn the driver of a burnt bulb by flashing together if a bulb is burned. This is why the L indicator is connected to the right side and visa versa. Notice in the diagram below that the flasher relay has a 2nd coil driven by the turnsignal current.

When changing to LEDs, the OEM flasher will sense LED turnsignals as burned out and will not drive K/C2 to 12V. Thus the L and R indicators are just in series and power the opposite side turnsignals.

EP26 is commercially available and is LED compatible although the K/C2 pin is open inside. This pin needs to be grounded to work properly. I resell EP26 with this pin grounded and show how to ground it yourself on my website.

[Harpo]

Thanks for the info but what about 911 1974 and on?

[spoke]

Originally Posted by Harpo

Thanks for the info but what about 911 1974 and on?

I am not sure when the 911 stopped using this scheme. My '86 930 did not have that connection.

[Classic 911]

Originally Posted by spoke

I am not sure when the 911 stopped using this scheme. My '86 930 did not have that connection.

Your solution on this issue is great spoke, it worked out just fine on my 1978 911SC also. I soldered a wire on my EP26 relay like the pictures on your web site shows. I have LED’s in all 6 outside indicators and use regular bulbs in the tacho indicators and everything works as it should, included the hazard function.

Thanks a lot


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[ToplessTarga]

What did your website Spoke?

[spoke]

Originally Posted by ToplessTarga

What did your website Spoke?

On my website, go to 'more' then 'Tech Articles' for info on how to mod EP26 to work for the older 911's, 914, and 912.

My website is: www.spokeworksled.com

[Craig_D]

Hey Spoke, I just ordered the EP26 relay from your site. I've been having the dual blinker syndrome on my '78 SC with the 1157 LED turn signals (fr/rr), and looked here for some answers.

Much appreciated.

Cheers,

- Craig_D

[spoke]

Originally Posted by Craig_D

Hey Spoke, I just ordered the EP26 relay from your site. I've been having the dual blinker syndrome on my '78 SC with the 1157 LED turn signals (fr/rr), and looked here for some answers.

Much appreciated.

Cheers,

- Craig_D

Got the order. Should go out Saturday. One thing, it's likely that the opposite tach indicator will flash. This is because the OEM flasher connects the common connection of the indicators to 12V and EP26 ties these to ground. The easy fix is to pop out the tach and pull out the entire indicator fixture like you were going to change the bulb and just put them in the opposite positions. Do not try to swap the wires.

[Craig_D]

Originally Posted by spoke

Got the order. Should go out Saturday. One thing, it's likely that the opposite tach indicator will flash. This is because the OEM flasher connects the common connection of the indicators to 12V and EP26 ties these to ground. The easy fix is to pop out the tach and pull out the entire indicator fixture like you were going to change the bulb and just put them in the opposite positions. Do not try to swap the wires.

Thank you, I did receive it! I have guests in town until Sunday, so I'll work on installing and testing it then.

Thank you for the product and the installation tips. I can't wait to try it out!

Cheers,

- Craig_D

[spoke]

Originally Posted by Harpo

Thanks for the info but what about 911 1974 and on?

I used Pelican's parts catalog to see when the 911 changed from the 4-pin flasher relay driving the tach indicators to a 3-pin flasher relay. Based on Pelican's catalog, 911's up to '84 use the 4-pin flasher relay. 85 up to '89 use a 3 pin relay. For LED-compatible relay for the later 911's, the EP36 is a drop in replacement. I have one on my '86 930.

[Craig_D]

Hey Spoke, I did the install and did need to swap the signal lights in the back of the tach.

It works great!

Thanks a ton!

- Craig_D

[chauser]

Not to derail the thread, but I have a 73.5 TS flasher issue as well.
I have LED rear brake lights (spokeworksled) but all turn signals are tungsten.
My flasher has started to work intermittently - when it fails, so does emergency flasher.
I can move flasher unit in its socket and get it to work, but then it fails again.
I've checked grounds at front battery boxes and they are OK.
I picked up a new flasher from our sponsor, and got odd results:
- flashers ON when no turn signal engaged
- correct turn signal ON when engaged

Would EP26 mod address this issue?
Charles

[spoke]

Originally Posted by chauser

Not to derail the thread, but I have a 73.5 TS flasher issue as well.
I have LED rear brake lights (spokeworksled) but all turn signals are tungsten.
My flasher has started to work intermittently - when it fails, so does emergency flasher.
I can move flasher unit in its socket and get it to work, but then it fails again.
I've checked grounds at front battery boxes and they are OK.
I picked up a new flasher from our sponsor, and got odd results:
- flashers ON when no turn signal engaged
- correct turn signal ON when engaged

Would EP26 mod address this issue?
Charles

So you haven't changed anything WRT turnsignal bulbs, correct? All are incandescent?

I'm confused about '- flashers ON when no turn signal engaged' What is flashing with no turnsignals?

[chauser]

Yes, all turn signal bulbs are tungsten.
Re flasher:
I can be obtuse ��

With original flasher in place, TS will work for a short while then not work at all, no emergency flasher either

I can get TS to work again if I pull on flasher while in socket.
I sprayed contact cleaner on socket and relay- no change in behavior

I picked up what is listed as replacement : wehrle E49, 54 201 102 A
When I put that relay in, turn ign on and do NOT engage TS, all corner lights flash as do indicators on dash

When I DO engage TS (ignition on) I get correct behavior, ie if I turn on left TS, I get only left TS, etc

Hope that helps

Many thanks
C

[Bill5900]

Spoke, will your LEDs work on all front and rear lights for a 1968? Thanks. Bill

[chauser]

Spoke,
I’m still trouble shooting my TS puzzle.
I picked up an EP26, and soldered wire as you described-thanks!
With Hand brake off, ign on the TSignals work (indicator lights are reversed as you state)

But, when I turn TS off, I still hear relay clicking - no TS are flashing though?

Any thoughts?
73.5 911

[spoke]

Originally Posted by Bill5900

Spoke, will your LEDs work on all front and rear lights for a 1968? Thanks. Bill

Bill,

I think the '68 has the same rear lights as the '69-'89 so yes my LEDs will fit your car.