78 SC Hazard lights and turn indicator problem
 

Thread update. For whatever reason some people never post the fix. Problem resolved, I had single filament bulbs in the turn signals, they need double filament bulbs one filament for the parking lights and one that blinks. Don’t think it can’t happen to you.:). But don’t stop reading, there is a lot of great troubleshooting and revelations from Dennis the wire guru in this thread that should help anyone with turn signal or flasher problems. Perseverance, don’t give up and the problem is almost always never what you think it is.


Please help. I’ve done a bit of troubleshooting and not sure what to check next.

The car is a 1978 911 SC USA.

I just rebuilt the pedal cluster, replaced the master cylinder brake switch, changed out the shifter and coupler, resurfaced the flywheel and replaced the clutch, and the car is running like a beast, but now I’m having light issues, I did replace the transmission and alternator grounds.

I do not know when the lights last worked right. I have checked the grounds and I have tried three new hazard relays. I have cleaned and inspected the turn signal switch (not really sure how to test it, or if it could be the problem).

The cars brake lights and headlights, horn and dash lighting are working normal but the hazards and turn signals are not.

1. Hazard light issues;

When the hazard button is on -

Hazard’s light solid with key off, lights off or on.

Hazards light solid with key on, lights on.

Hazards blink (normal) with key on or run, lights off.

2. Parking light issues;

When the light switch is on - and key is off, on or run - right side parking lights and license plate lights come on. The left side does not light up.

3. Turn signal issues;

When the light switch is off and key is off, on, or run the turn signals don’t come on at all regardless of the turn signal selector lever position.

When the light switch is on both dash indicators light up, when I signal right, the indicators and lights goes from solid bright to brighter. When I signal left the indicators go out, but the left side external lights come on solid (not flashing).

I have verified the connections of my light switch they match;

http://forums.pelicanparts.com/uploa...1625950765.jpg


I have tested the function of my light switch at the switch terminals-see chart;


http://forums.pelicanparts.com/uploa...1625950954.jpg

The only thing I have found questionable is an empty piggyback jumper on the headlight wire, I think it’s a left over from the alarm system that was removed decades ago, see picture;

http://forums.pelicanparts.com/uploa...1625953668.jpg

What next?SmileWavy

Did you check relay?

Check all your bulbs and connections, rear can get pretty crusty,

Yes, I checked the relay I have four, the original and two new, they all work the same. Yes, all the bulbs and connections are clean and work when they get power.

I had a similar problem with weird turn signals. It was the wiring going into the 4 way flasher, my mechanic went over the connections and some were loose.

Use the correct drawing for your year and confirm wiring perhaps?
https://www.dropbox.com/s/yjfoxfvwlci6lys/911_electrical_78SC_USA.pdf?dl=0

Dennis, thanks for the diagram. I pulled everything and there was a black white wire disconnected, I connected it and the hazards flash now. All the wiring looks right.

Still have one issue remaining.

I’ve narrowed down the issue to the grey red dashed wire connected to 58R at the light switch. Everything works as normal when the light switch is off.


When the light switch is on, the right parking lights come on solid and both turn indicators are lit. If I disconnect the grey red dashed wire all the parking lights and indicators go out.

I’m getting closer. I can at least drive during the day with turn signals now.SmileWavy


http://forums.pelicanparts.com/uploa...1626060138.jpg

Also check out this thread for some nice air filter covers you might like to use for your build.

http://forums.pelicanparts.com/porsche-911-technical-forum/1095416-k-n-filter-measurements.html

You may want to go up front to the trunk and verify the fuse box wiring as well. Grey/red and grey/black are the running light circuits. Black white and black green are signal lamps.
Are both front and back lights acting the same? If just the tail light, could be internal to it.

Yes both the front and back are acting the same, the problem is isolated to left and right, and only when the headlight switch is on, not front and back. I’ll double check the fuse box.

Remember to count the fuse position (S) from the headlight back when using the Porsche factory drawing. (Closest to headlight is one)
The 78 color schematic is nice as each fuse is colored for the fuse size as well. :)

Any bumper changes recently? Easy to cross wiring there as wire colors change from headlight bucket to bumper lights.

Yes, the front right fender and headlight was replaced. I’ll look there again.

Update; Still haven’t got it.

Found and fixed two issues, a short at the rear left reverse light wire pinched between the light housing and cover. And bulbs in the wrong sockets. So a couple of problems went away.

Still have this problem; When the light switch is off everything works as normal. However, when the light switch is on, the turn signals light up bright solid but don’t blink with the hazard button or left/right turn signal, and the dash turn indicators don’t light up or blink.

Have you pulled the relay behind the fuel gauge and tested it?
But then again, it works normally (flashes) with light switch off, but not with light switch on.
Maybe check wiring from 58a of light switch to N6 and then to
58 on the hazard switch is all correct. Also check the ground is electrically good on the relay base.
Could be a voltage loading problem (voltage drop that stops relay from operating) due to poor grounding in the circuits for the lighting and flasher.

Yes, I pulled the relay. I have the original, plus three new relays they all do the same thing.

Yes, 58a goes to the resistor (N6) and then to 58 of E3 hazard switch.

I have checked the relay functions at the base, but not with the light switch on. I’ll try that, thanks.

Thanks for staying with me, As you describe it voltage loading and poor grounding problem sounds likely. I’ve checked the grounds you’ve mentioned.

The relay base 31 goes to a solid ground.

On the hazard switch 31 goes to a solid ground.

I don’t see a ground from the light switch.

I did find a cut wire near the front fuse holder (see picture below) but don’t see the other end, is the ground wire shown original or an aftermarket hack?

http://forums.pelicanparts.com/uploa...1626568939.jpg

Doesn’t look original. Brown is ground on original wiring.

Some suggestions:
Check grounds at each lamp fixture and the Tach gauge along with the turn signal harness.
Confirm every wire lands where it should on the hazard and light switch.
Does the dimmer function for dash lights on the light switch work?
Maybe try removing bulbs one at a time with lights on and flasher activated to see if it starts working?
So strange that it works otherwise.

Yes, the dimmer function on the light switch works and all the bulbs dim including the hazard switch. I’ll double check the wires at the hazard and the light switch. I’m not sure what I’m looking for on the tach ground. Is it a brown wire from the tach to ground? I’ll look it up.

Never mind the Tach ground, just recalled those bulbs are isolated from the housing.

It really seems like a wire is in the wrong spot, somehow removing voltage to the flasher unit when initializing the headlights.

This wire was wrong, I think it’s right now as shown. Why are the end connectors different? One is clear and the other is black.

The black/white/green wire comes from E3 (hazard switch) pin 49a, and connects to the black/white wire that runs to E2 (turn signal) pin 49a.

http://forums.pelicanparts.com/uploa...1626648247.jpg

Still working, haven’t hooked up the juice yet.

I’m not sure about this one. The solid grey wire comes from D (ignition switch) and it is plugged into a solid grey wire going to E1 (light switch).

Again, the end connector insulation’s are different one is black and one is clear. I had this grey wire and the black green white wires opposite before. It seemed like the end connectors should have matched up, clear to clear, and black to black. Maybe that was the problem.

So it’s like this now.

http://forums.pelicanparts.com/uploa...1626649196.jpg

These two matching thick yellow wires look like they should connect?I had then connected. I don’t see them on the diagram.

http://forums.pelicanparts.com/uploa...1626650289.jpg

Yellows are for other options/countries.
No comment on the connector cover colors. You’d have to ask the people that made them. :)
As long as you are sure your connections are right, might as well give it the juice…

I just checked the fuses before adding the juice and a couple are blown (parking lights), they must of been like that from before I made changes. Problem is I don’t have any of the replacements, I’ll get some tomorrow and see if I can’t make it work.

Still the same problem. When the lights switch is on the hazards and/or turn signals don’t flash. And it doesn’t matter what configuration I plug the wires in that I identified yesterday, the problem is the same.

There was a wire reversed on the right from side marker, that’s fixed.

I’m still not sure about the grey wire, it is hot when the ignition is off, and off when ignition is on or run.

I also tried removing lights while the lights and flasher were on, no luck, they never flashed.

The fuses are not blowing and all the lights work but don’t flash when both switches are on.

This might be something …. The small bulb in the headlight housing (parking light?) under the main bulb has a ground (brown wire) attached to the holder, but no wire for power. It’s the same on both sides, those bulbs don’t light of course, but I don't know where the power wires are, I’m assuming my car didn’t have that as an option?

Right side.

http://forums.pelicanparts.com/uploa...1626742033.jpg

Left side.

http://forums.pelicanparts.com/uploa...1626742033.jpg

City lights wouldn’t have an effect on the flasher.
Maybe it is in the actual light or hazard switch where a contact that should stay made isn’t?

An ohmmeter and a print and a plan, to test the functions and confirm every wire in the circuit including at the fuse panel is what you need to do.
Isolate, verify and keep at it to find what is not working.

Isolate (disconnect) the front right fender wiring by removing the appropriate fuses just to it, and see if the problem goes away

I took out the 4 fuses to lights on the front right, same problem. So then did the left fender, then both, then all front and rear, no change.

I think that the problem is internal to the light switch, specifically when it is in the on positions.

Time to go shopping I think.

After a few days of not thinking about it, I have got back at it. It probably isn’t the light switch so I’m moving past that.

The problem is isolated to the parking lights, if either the left or right, parking light fuses are in I have the issue with the hazards and turn signals going solid when signal, or hazard and the light switch is on, (It does this if the rear lights are connected or not). When I disable the parking lights by pulling the two fuses, the hazards and turn signals flash as normal.

More to follow.

Do you have any led lights installed?
Just curious.
I agree it isn’t related to the switch, sounds like a wiring issue up front.
Maybe isolate the parking light wiring at the headlights with the fuses in, to see if it is past the headlight connectors.

I don’t think I have LED’s. I replaced all of the lights including the dash lights, excep for the small indicators lights in the tach, I can’t tell for sure, should I just pull them out?

No. Leave as is. The problem has shown itself to be in a specific circuit.

Update. Things I know now that I didn’t know before. Reference pictures in post #21-23.

The yellow wire from the turn signal plugs into the yellow wire, back to the turn signal, it is the low beams. Low beams don’t come on without it being plugged in.

The grey wire from the ignition goes to the grey wire to the headlight switch. The grey wire is hot only when ignition is off.

The green/black wire from the hazard switch plugs into the green/black wire to the turn signal switch.


!!! The green/black wire flashes my test light when the ignition is on, when nothing else is switched, the corners and indicators don’t come on or flash. This is weird and probably isn’t right.

How do I check for proper ground at the flasher relay?

Use an ohmmeter to test the relay base for ground continuity.
Ignition off, battery disconnected.
Remove relay, (using the wire entry to the base as 6 o’clock for orientation)
Insert one of the meter probes into the relay base socket at either the 3 or 9 o’clock position (can’t remember which one right now, one is ground the other is power)
Other meter probe to a good ground.
Should read less than an ohm on the ground wire.

Ok , it looks like 3 o’clock is the ground which goes to pin 31 of the relay. Tested with power disconnected and key off.

3 o’clock = 0.0
6 o’clock= 7.5
9 o’clock = 2.5
12 o’clock = 0.L (nothing)

Test lamp with power on at the relay pins with the hazards on.

3 o’clock, 31 pin = nothing
6 o’clock, C pin = blinking
9 o’clock, 49 pin = solid
12 o’clock 49a pin = blinking

And with the hazards and the lights on.

3 o’clock, 31 pin = nothing
6 o’clock, C pin = weak solid glow, barely visible.
9 o’clock, 49 pin = solid
12 o’clock 49a pin = solid

This is weird. Do you have headlight relays installed? Maybe it is something in the hi/low signal switch if not.
Can you take and post a photo of the top and bottom wires on fuse 9 and 10? (counting back from the headlights)
Also confirm Black/white and Black/green go to the center of the signal lamp bulb.

There are posts here where guys have had problems with the flasher unit ground and jumped 2 terminals on the flasher, but I don’t think they had your unique situation of it only stopping with headlights on.

I do not have headlight relays installed. Will take pictures and make the checks you mentioned.

Just one last question. Was it all working normally before the right side fender was replaced?