1986 911 Carrera signal light issues

[Vancity911]

Hi guys

Im going nuts trying to troubleshoot an issue that came up in the last few days where my passenger side rear signal light isn't working.

Ive checked and confirmed all bulbs are fine...

both front and rear signal lights on driver side work fine

The passenger side front signal works fine

all parking/running lights work fine as well as headlights low/high beam

ive confirmed all related fuses are working (9 & 10)

The green signal lights on the dash work fine and no irregular timing so I think the relay is fine.

Hazard lights work fine.

Im wondering if it might be the strange diode people have mentioned that exists on the 86 carrera?

gonna try and find it under the dash and test it with a multimeter

[Schulisco]

My guess - a contact / ground connection problem.
As you can see in the wiring diagram below - the ground of the right rear turn signal is connected to the right rear light. I would search at this point for an issue.



The only diode I know is that for the interior light:



Thomas

[Vancity911]

Thanks Thomas!

going to troubleshoot the ground

[Vancity911]

im still stuck on this. all parking lights and front right signal light works - its just the passenger side rear signal light I can't figure out.

I removed the light fixture and cleaned the signal socket and tested it but no power

[timmy2]

Check the grey/red and grey/black wires at the light switch. One of them will have the diode. (No print handy so I’m not sure which)
Just bypass it to see if that cures the problem.

[Vancity911]

Originally Posted by timmy2

Check the grey/red and grey/black wires at the light switch. One of them will have the diode. (No print handy so I’m not sure which)
Just bypass it to see if that cures the problem.

you mean on the headlight switch or the turn signal stalk?

I only found one diode, it was burnt out, I replaced it with a new one but still no luck

[86 911 Targa]

The pic you posted is the one that I posted a while back.

Let's work this on a pm basis, or, if your phose will reach the U.S., we
can talk.

I have the factory circuits for the '86.

Gerry

[Vancity911]

So I inspected and tested the rear wire harness connector (passenger side) on the inside of the engine compartment..

discovered there is no power sending to the turn signal light so that ruled out the actual light fixture socket or its cabling being the culprit.
(I also tested the driver side connection which is working and of course it was sending pulsating power to the signal light)

since my right front signal light works and all other signal lights im not sure if the problem would be the signal light relay but im going to replace it just in case

I should mention the signal light stalk works fine and displays both left and green lights flashing properly

[Vancity911]

just had a look at the relay

looks like it only has left and right side terminals for the signal lights and 1 for the hazard flashers so front/back share the same voltage path

this would most likely rule out my problem being this since the passenger right front signal light works

(driver side both front and back work)

[timmy2]

Loose wire in the fuse block?
Check continuity to the 6 pin at the rear.

[Vancity911]

Originally Posted by timmy2

Loose wire in the fuse block?
Check continuity to the 6 pin at the rear.

ive ruled out any issues with the fuses or fusebox- -front right signal light works fine.

the signal light pin isn't sending power or voltage on the connector that connects to the rear light fixture (in the engine compartment) all the other pins are sending proper (backup, brake, parking lights)

I made sure to also check the left driver side which is working just to be sure and confirm - it of course was sending proper voltage to the signal light pin

[timmy2]

Describe what you see top and bottom of fuses 9 and 10 counting back from the headlight.
Black/white wires are passenger side signals.
2 wires on top and one on bottom?
The pulse signal comes in on the top of the fuse from the relay and goes out to the rear in the same terminal. (Unfused to rear) the signal goes through the fuse on the bottom to the front signals.
I think Porsche designed it like this so that a blown fuse only affects the front and not the rear for safety.
I would undo the top fuse screw and take a good look at the 2 wire ends.

[timmy2]

Color diagram from 78 illustrates what was done for all years from 70-83 that I am sure of. Likely the same for 86. S9 and S10 are the fuses as counted from the headlight towards the driver.

[Vancity911]

Originally Posted by timmy2

Describe what you see top and bottom of fuses 9 and 10 counting back from the headlight.
Black/white wires are passenger side signals.
2 wires on top and one on bottom?
The pulse signal comes in on the top of the fuse from the relay and goes out to the rear in the same terminal. (Unfused to rear) the signal goes through the fuse on the bottom to the front signals.
I think Porsche designed it like this so that a blown fuse only affects the front and not the rear for safety.
I would undo the top fuse screw and take a good look at the 2 wire ends.

Will check this tomorrow and update. thanks for helping me out!

[timmy2]

I misread your original post, thought it was the running light out, that was the diode reference.
Signals have no diodes.

This is what I was thinking…. Getting old I guess…
https://forums.pelicanparts.com/porsche-911-technical-forum/1099182-passenger-side-parking-running-lights-no-workie.html

[Vancity911]

Originally Posted by timmy2

I misread your original post, thought it was the running light out, that was the diode reference.
Signals have no diodes.

This is what I was thinking…. Getting old I guess…
https://forums.pelicanparts.com/porsche-911-technical-forum/1099182-passenger-side-parking-running-lights-no-workie.html

all good!

you were 100% right about the signal light issue - it was the 2 black and white wires on top of that #9 fuse - they looked pretty rough - clipped and stripped, back in and voila, turn signal works perfect now

Really appreciate your help, I owe you a case of beer!

[timmy2]

Happy to help.
Glad you found it and fixed it.
You should at a minimum tin the wire ends with a little solder, or install some new wire ferrules.
The bare copper will compress over time and get loose again.

[Vancity911]

Originally Posted by timmy2

Happy to help.
Glad you found it and fixed it.
You should at a minimum tin the wire ends with a little solder, or install some new wire ferrules.
The bare copper will compress over time and get loose again.

great advice. I will fire up the soldering iron tomorrow and tin them!

[Schulisco]

Great to hear that you found it! But I urgently recommend not to tin the cables in the fuse box. Instead you should use ferrules as Porsche did originally. If the tinned cables heat up the tin can run away and shortcut anything else...also the thinned cables aren't flexible any more while being fixed in the fuse holder and they can break over time...

Thomas

[lrodri64]

Are you using led lamps ?
I had a similar situation with a customer 911 and it was caused by the led lamps installed.