How do the turn signals work?

From alt.autos.studebaker
I'm doing my own wire harness for the 53 Sedan I'm restoring. I'm struggling with the turn signal connections now. I rebuilt the steering post column completely and put a 6 wire connector on the puppy. I have a wiring diagram and am fairly competent in electronics, but I still can't figure out how they get turn/stop/running lights (3 functions) using a 2 filament bulb. Can anyone explain it to me?

Robert Kabchef: David, Surely you're aware that the T/S switch serves to isolate the rear bulb's stop filament from the brake light circuit and use it as the blinker, no? In other words, when the turn signal switch is centered, the brake light switch sends power to it and through it's contacts (the T/S switch) to the two brake light filaments. These early 50s cars, the T/S system was still an option. but looking at the parts book shows the same taillight harness for all 53s. That would make me think that you need to reconfigure the wire arrangement under the dash to accommodate your T/S switch. On my '51, it seems I recall that there WAS a second bulb incorporated to give the turn signal function. Right now I'd be hard pressed to dig out the tail light bodies to confirm that for you.

Paul Villforth: Mr. Dave, The stop and turn signal uses the same filament. Replacement harnesses from Studebaker used plastic coated insulation. I got one for my 51 back in 1970 and it was plastic insulation and was a Stude original. So your 53 would be original with the correct color coding. I have a drawing on how to hook up the dash indicators and it is just the opposite of the way you think it should be. If you look it up the logical way it will not work correctly. If you go to a NAPA store ask for 720524 bullet terminals. They are exactly the same as the ones Studebaker used.

Hopman Jeffrey: Forgot to mention in the previous note that I did have a lot of trouble with the flasher. My car now has a "late model" fuel injection engine in it that I am working to get hooked up. So, all the accessories are going to be 12v. I got a electronic flasher to use and had a problem getting it to work. Near as I can figure, the original flasher setup had it so the blinker lamps on the dash were "grounded" through the front turn signal filaments. I think what was supposed to happen was the dash blinkers would come on when the outside ones were off and vice-versa. That way if a bulb was out on the front signals, the dash one would not come on and you would have a bulb out warning of sorts. The way my electronic flasher was setup I did not get that to work so they now come on and off at the same time as the fronts. I had to rewire the flasher socket too and the pin out was different and it would not work the first attempt. This had nothing to do with the signal switch itself.

The Five Wire Multiple Connector Pin Out
The factory shop manual is lacking in this area, no color code was given for the Directional Signal Switch. The image below is a composite of the shop manual with the photos taken of my rewired unit.


The top center photo show what's inside the switch. It contains two triangular brass plates mounted to a prestolie base. This base is free to slide on a spring incased rail. The spring holds the two triangular pads apart and in the neutral position. When you signal a turn, one of the pads will move toward the center of the assembly, creating a different circuit combination. The photo to the right, shows the assembled unit with the new wires attached. From the assembled unit I buzzed out the following connections below. The following table does not show the break light logic, just the turn signal logic:

Direction Blue Green Brown Yellow White Red
Center Stop Stop   Stop    
Left   Stop Flash Flash   Flash
Right   Flash Flash Stop Flash  
Destination Stoplight output
#16 Red&Wh.
Right Rear
#16Green&Wh.
Flasher output
#16Black
Left Rear
#16Brown&Wh.
Right Front
#16Green&Wh.
Left Front
#16Brown&Wh.

So how does the turn signal work?
So the question is how do you make a two filament bulb do three things, stop light, park light, turn signal. Robert Kabchef says they make the stop light do double duty? Another question is why do the left/right pilot light have two wires going to them. Lets look at the rear light logic on a case by case basis.

Case1: Day driving, not turning and you hit the breaks?
From the wiring diagram above, the stoplight switch gets it's power from the auxiliary circuit breaker. When you hit the brake pedal, the voltage is applied to the 5 wire connector through the #16 Red/White wire. This is patched into the Blue wire on the direction signal switch. The copper triangular pads are in the neutral position so the Green and Yellow wires now have voltage. These wires go to the two rear bulbs, giving us break lights.

Case2: Day driving and turning left?
When you turn left, the copper triangular pad in the signal switch breaks the Blue-Yellow connection, taking the stop light function away for the left rear bulb. At the same time it creates a connection between Yellow-Red-Brown. The flasher outputs an on/off voltage through a #16 Black wire into the Directional Signal Switch via the #16 Brown wire. This voltage is then sent to the Red and Yellow lines to the front left turn light and the rear left turn light respectively via the #16 White/Brown and #16 Brown/White wires shown. This causes the left turn lights to pulse using the brake light filament.

Case3: Night driving, not turning?
This is the simple one, the headlight switch sends power to the driving light filament via the #16 Black/Oak wire. What the wiring diagram doesn't show is that the headlight switch also sends current to the front grille bar lights, they also have two filaments. These filaments do only a single function.

Case4: Night driving and turning left?
Like Case 3 above, the headlight switch sends current to the driving light filament via the #16Black/Oak wire, and the Case 2 logic drives the stop/turn signal filament.

Case5: Night driving and turning left at a stoplight?
Like Case 4 above plus the stop light switch is sending current through the Blue-Green connection. This means that the driving filament is on for both lights, you have a solid right stoplight filament, and a flashing left stoplight/turn filament.

Why do the dash turn indicators have two wires feeding them?
The wiring diagram shows the right pilot light and the left directional signal light are connected via the #16Green-#16White/Brown wires. To further complicate the matter, the right directional signal light and the left pilot light pair up also. Then both of these runs share a common terminal on the flasher module. What gives??? The diagram show the flasher unit gets it's current from the ignition switch, but how does it get the ground to make the flasher operate???

LGeoCole: The dash lamps get power from the flasher. That's  the high side. The low side is the front turn signal  lamp that's not being used. The T/S lamp takes a lot  more current to light than the dash lamp so most of  the voltage shows up across the dash lamp. The dash  lamp glows, but the not-turning-side T/S lamp doesn't.  If it weren't hooked up this way, you could only have  a single dash lamp unless the switch were more  complicated. Sound OK? The idea from "Hopman Jeffery" idea makes sense. If a  front lamp is out, the dash light for the other side  won't work causing you to look for a problem, maybe.

Greg Hodge: I have been lurking this NG for about 14 months... Most enjoyable (mostly). Time for a "Pay Back". Albeit a Long one.
>>Could someone verify my logic in the case1..case6 dialog?<<
Seems correct to me. The logic diagram is the key. Nice Job. But... Let's simplify it a bit. (As I understand it.)

An 1157 is a 12V dual filament lamp. One filament draws about .6 Amp (low power Park / Tail filament) and the other about 2 Amps (high power Brake / Turn filament). Let's say a dash indicator lamp draws .25 Amp. (all @ 12 Volts). Tail (and Park lights as they used to be known as in my youth) are a completely separate circuit from the Brake / Turn lights. Off, they're off. On, the lower power filaments are lit. Step on the brake (nothing else is on) and the brake light switch supplies power to the rear high power filaments. (Brake lights on.)

Now for the complications... Add a turn signal switch and a flasher.

Flasher: I have not investigated a 3 terminal flasher, but that won't stop me... A 2 pin flasher starts as a "closed" switch; power in one terminal goes through to the other. But, the power also goes through a "heater" (a serial circuit) that heats up a bi-metal strip that gets hot, bends and "opens" the switch. No current through the heater when the "switch" is open, the heater cools, the bi-metal cools and closes the "switch". This switch is the click - click of the flasher. Electronic flashers use a simple electronic circuit and relay to "click". The relay carries the current to the lamps. The electronic component(s) *mostly* determine the click timing, that's why electronic flashers work with or without the extra load of trailer lights where *some* flashers don't work so well.

Turn Signal Switch: This switch switches the 4 high power filaments at the 4 corners. It does this by switching (all separately) the Rear (high power filaments) to either the flasher or brake light switch; and the Front (high power filaments) to either the flasher or an *open* circuit.
Not turning... L & R (rear) brake (high power) filaments are connected (in parallel) to the brake light switch. (Just like the real old days.) Front (high power) filaments are not connected to anything (open circuit).

Left Turn: Right Rear high power filament is still connected to the brake light switch. (Right Rear brake light operates normally via the brake light switch.) Right Front high power filament is not connected to power (no change). Left Rear high power filament is connected to the flasher (flasher blinks lamp). Left Front high power filament is also connected to the flasher (ditto).

Right Turn: Uhmmm... "Mirror Image" of above.

>>Also why are there two wires going to the dash pilot lights in the factory diagram?<<
Now, to the original question... The tricky part...Both dash lights get their *Flashing* power from the flasher. (in parallel) Now, note that the second terminals on the dash lights go to the OPPOSITE FRONT Turn (high power) filaments. That's right, the Left indicator lamp gets it's GROUND THROUGH the RIGHT FRONT (high power) filament.

Huh... What??? OK, you put a lamp that takes .25 Amp to light up IN SERIES with a lamp that takes 2 Amps to light... The lower power lamp limits the current in the circuit to say .25 Amp. The smaller lamp lights, the high power lamp filament might get warm, but Not Hot Enough to Light Up. Remember, the Right Front (high power) filament is not connected to power.

And... The Right indicator also has the flashing power applied??? Correct, BUT the *other* (ground) wire for the Right indicator goes to the LEFT Front (high power) filament which also is connected to the Flasher Power. Both terminals of the Right indicator lamp are at the same (flashing) voltage at the same time. Both terminals are either *Hot* or *Cold* at the same time. No *instantaneous* voltage ACROSS the terminals... No Light. Questions anybody? Greg

So how do you bench test the flasher circuit?
Now we move on to how do we bench test the unit. I've got the flasher assembly rebuilt and the instrument panel. I stick the pilot lights into the dash after testing them, ground the dash, and apply current to the IGN connection on the flasher assembly. I assume I should ground out the offset connector on the pilot lights right? Do I have to connect the flasher pulse out line to the T/S indicator? My goal is to get the pilot lights to flash and measure the current draw from the flasher assembly in this state.

Greg Hodge:> I assume I should ground out the offset connector on the pilot lights right?
Nope, not if those are the turn signal dash indicators. They look like the grounds are isolated (from the dash). The schematic says that the dash pilot light "grounds" go to the opposite (left-right) Front high power filaments. The other terminal of the high power filament goes to ground. This is that confusing low power / high power lamps in series circuit.

> Do I have to connect the flasher pulse out line to the T/S indicator?
I'm unsure about which flasher terminal you are referring to. I will try to get a 3 terminal flasher to "examine" later. Basically, you have to mock up all 4 high power filaments to test both right and left. Three are needed to test one side. You need the load of 2 high power filaments to make the flasher work. Mock up (duplicate) the high power filaments and dash indicators and flasher as per the schematic. It should work.

Where can I get replacement flasher units, I toasted mine in this exercise?
NAPA