Does the turn signal switch work by completing a ground circuit or does voltage pass through it ?

Even if it is in the ground path, voltage still passes through it...

But it is in the "hot" leg of the circuit.

--DD

The turnsignal switch and hazard switch are between the flasher and the bulbs.

Power goes like this: +12V >> Flasher >> TS/Hazard switches >> bulbs >> GND

This may help describe the logic.

http://www.914club.com/bbs2/index.php?show...=47236&st=0

This is the best description of the circuit I have seen...as follows for later models 74 to 76.

Dave

"Hi Folks, well I'm back at it. I will go through this in 3 posts, maybe 4, so bear with me. Sorry if everyone already knew all this, but it was an epiphany for me, so maybe someone else didn't know some piece of this.

First, it's important to know how the flasher itself works. There's a schematic below.


There are three parts of the flasher. The primary relay (I'll call it) switches on and off and provides an on/off voltage to ANYTHING connected to it. This is controlled by the second part, a solid state timing circuit. When a load is detected, the timing circuit starts pumping out a little square wave to the coil of the primary relay, causing it to turn on and off.... By doing it this way, the frequency of the on-and-off is independent of the load, because the load on the timing circuit (ie, the relay coil) is always the same.

Now it gets interesting. Notice that the output of the primary relay actually passes in series THROUGH the coil of the secondary relay. This coil is a special kind of coil that is normally used in magnetic circuit breakers rather than relays. It is a CURRENT COIL, and the secondary relay will close only when enough CURRENT is passing through it. Relays generally have voltage coils that close when the correct minimum voltage is applied. The current coil is designed to minimize voltage drop, so it is only a few turns of relatively heavy gauge wire.

After it has passed through the coil of the secondary relay, it exits the flasher to be used for anything in the car that needs to flash- directional signals, hazard warning, emergency brake light, or (at least in my car) the fasten seatbelt light.

The secondary relay will create a second flashing output, but only if enough current is passing through the primary flashing relay. The threshold current that trips the secondary coil will cause a secondary flashing output when the turn signals or the hazard flashers are engaged, but not when the emergency brake light or the fasten seatbelt light is engaged. They still flash because they are attached to the primary relay, which is oblivious to load, but their load isn't enough to cause the secondary output to flash.

Why bother? Well, the law required a cockpit-visible indication of a burned out direction signal bulb. So if you turn on your left signal and the front bulb, say, is burned out, the rear signal will still flash, but there will be no secondary flashing output. And, you guessed it, the secondary flashing output goes to the indicator light on the dash.

You can actually hear it if you sit in your car with the engine off, but turn the ignition on. Pull up on the emergency brake and listen, and then turn on one of the direction signals. The click gets audibly louder because both relays are clicking instead of just the one.

I drew the '73.5-'76 circuit first, because it's easier to figure out. This secondary flashing output goes directly to the only turn signal indicator in the tach (via the blue/white wire). The other side of that indicator is grounded.....

So, the driver-visible indication of a burned out bulb is- when the turn signal indicator works fine for one direction, but remains dark when you switch to signal for the other direction.... There is a bulb burned out on the latter side. Or something else that can reduce the current flow below what is required to trip the secondary relay... Like corroded contacts, corroded socket, wrong type bulb (not bright enough), bulbs replaced with LEDs, whatever that reduced the current below the flashing threshold.

Next post- '70-'73.5. Somebody was on drugs when they figured that one out!"

Click to view attachment

Here for ease is the second description of early circuit 70-73.5

Dave


"All right. Back again. Here's the schematic for the '70 - '73.5. These are the cars with separate left and right indicators at the top of the tach, and the high beam indicator along on the bottom...


Thankfully, the flasher works the same as in the later models that only have one indicator, which was covered in my earlier post.

When you look the indicators, it gets weird- The same blue/white wire goes to the tach, and it hooks to BOTH bulbs. The other lead of each bulb, instead of going to ground, actually goes to the turn signal circult that goes off to the bulbs themselves. BUT WAIT!!! The LEFT indicator is connected to the RIGHT circuit, and the RIGHT indicator is connected to the LEFT circuit.

If you study what's going on, you see it. When the left turn signal is on, the flashing signal trailing out to the bulbs is +12v/0/+12v/0/+12v/0 and on and on. The same signal is coming out from the secondary relay to both indicator lights. This signal is in phase with the primary flashing signal, so the indicator that is connected to the left turn signal WILL NOT FLASH because it will see +12v on both leads at the same time, or 0 on both leads at the same time. There will never be a voltage differential that will cause it to light up. And which indicator do you NOT want to see flash when the left signal is on? That's right- the RIGHT one.

So what happens with the left indicator? It flashes! Because one lead is connected to the same secondary flashing output that the other indicator is connected to, but its second lead, which is connected to the RIGHT signal circuit IS GROUNDED THROUGH THE TURN SIGNAL BULB FILAMENTS THEMSELVES! (let sink in)

This grounding scheme works because the indicator bulb is much lower wattage (meaning much higher resistance) than the main signal bulbs, so it lights up and limits the current in the circuit to a level below which the main bulbs turn on.

So that's pretty tricky, but it's not over yet! What happens when a bulb is out? Well, the secondary relay in the flasher stays open, as before. But what a weird-ass result that has- BOTH INDICATORS FLASH TOGETHER when the side with the missing/wrong/corroded/LED/whatever problem is turned on. (IMG:http://www.914club.com/bbs2/style_emoticons/default/WTF.gif)

If you look at the circuit, you can see what's going on- with the output from the secondary relay floating, you have both indicator bulbs, in series, completing the circuit from the side that's on (+12v or thereabouts) to the side that's off, and grounding through the filaments of the big signal bulbs again! The indicators are a bit dimmer, because they're wired in series, but they flash together.

If you replaced your indicators with LEDs, this cannot happen. The back-to-back series LEDs will block current flow. In this case the indicator that a bulb is out is that the indicator LED on the side with the bad bulb will remain off when that side's turn signal is turned on.

So that's about it. These two installments show the before and after circuits for incorporating early dual indicators into late tachs... Plus enough info to dispel myths that are drifting around about grounding problems, diodes in the harness, etc, etc, etc.....

You can now also figure out how to diagnose problems better. For example, if the dash indicator light is on, but doesn't flash, it has to be a bad flasher. If the signals flash, but the indicator is steady, it's the secondary relay in the flasher. If both stay on, it's the primary relay in the flasher (probably) or the solid state timing circuit in the flasher (unlikely). etc, etc, etc...."

Click to view attachment

Thanks for those; I forgot that back in 2006 I had reworked the indicator lights on my late car to seperate dash lights.....

My follow up question: Does the early 911 wiring for the TS switch follow the same pathways and wire color coding: same for Wiper switch.

I'm still learning the 911 turnsignal schematics as I'm making front and rear LED turnsignal boards for '69-'89 912/911/930 and the existing flashers hyperflash with LED bulbs.

It appears Porsche used similar design practices throughout the years as they did with the 914. It seems they were trying to use the turnsignals as parking lights as with the 914 when the car is off and the turnsignal stalk is in the L and R position.

Unless someone has cataloged which years did what, the best bet is to get the schematic for the exact year you want and examine that.

Reason I asked is I may do the 911 conversion with the 911 TS and wiper switches along with the ignition switch and steering column. The Ignition switch was easy.....

Here is a diagram of the late connector. I could label three from your previous diagra and added two more from the PP wiring diagram .

Can anyone identify what slots 3, 4, 7, 8, 9. Based on the colors ?

#3: I'm not seeing gray or white at the switch on the wiring diagram. There's a gray wire from the headlight switch to the instrument lights, but it wouldn't be on the turn signal switch!
#4: Goes to the (single) turn signal indicator light in the tach.
#7: Possibly carries the horn signal; short it to ground and the horn may sound.
#8: Goes from the dimmer switch (pull back the stalk) to the high/low beam relay.
#9: Either the tach signal wire, or the wire from the wiper switch to the wiper motor.

Which connector is this? Because it seems like it has rather more than just turn signal wires in it.

--DD

Thanks Dave. I traced the gray wire back to the ignition switch.

I seem to remember that the gray wire activates the parking feature in the turn signal switch. It is only active when the key is removed, thus the connection to the keyswitch...

Jim,

3 = power to the parking lights
4 = power to the turn signal lights
7, 9 = horn
8 = Headlight dimmer switch