This may be a dumb question, but back in the day, how come people installed large fender mounted or bumper mounted turn signals. Why wouldnt they just wire into the parking lights. Alot of early cars had white turn signal lenses.

 

The parking lights only had one filament.

 

Well, that's not a dumb question at all. Who can say why people do what they do, but I have a theory:

If you wanted to add signal lights to your older vintage Ford Truck, usually you had to buy an aftermarket "Kit." If you have ever read a late 50s or early 60 vintage "Popular Mechanics" you would realize that "Kits" were the in thing. So when you would buy a signal light kit for your truck, it had to include everything...switch, flasher, lights, etc.

And usually they were installed as a kit - a separate system - rather than tapping into a stock system.

But there's a technical reason too. The light bulb sockets that supported just parking lights or running lights are physically and functionally configured differently. Normally the original light had a socket that was insulated, and had two wires - one for power to the light and one for ground.
And the sockets in the signal light kits were the same. So they could only function on one circuit. This light bulb had one filiment to handle that function.

Now, later when signal lights became standard, the sockets changed and so did the light bulbs. Since the light would now handle two separate functions - both parking/running lights; and, signals it needed to be able to do both at the same time. This was handled in the bulb by introducing a second filiment for the second function.

But more important (as you will continue to see in post where people are having trouble getting lights to work) the sockets had to be rededigned to handle the second filiment. Thus, they were wired with BOTH wires providing power - one to each filiment - and the BASE OF THE SOCKET WAS NOW MADE CONDUCTIVE TO ACT AS THE GROUND PATH FOR THE LIGHT.

So, if you wanted to add signals, you had one of two choices: either replace the original sockets to handle two filiment base grounded bulbs; or, install the lights provided with the kit! The original sockets would not support dual function.

And this may sound REALLY dumb, but I'm not sure they had invented or were commonly using the dual filiment bulbs and sockets back then....But that's purely speculation on my part!

Hope that helped!

PS, Edit note: I think Ross and I were typing at the same time. Doesn't he just go on and on - tee hee!

 

It is also because of the brake light circuit.

 

Yup that Ross sure said a mouth full didn't he lol

 

""So, if you wanted to add signals, you had one of two choices: either replace the original sockets to handle two filiment base grounded bulbs; or, install the lights provided with the kit! The original sockets would not support dual function. "

Would this third option work?......bypass the parking light circuit to the front parking light bulbs and just use them as turn signals. Keep the single filament bulbs.

 

I think you have another option if you use a Signal-Stat 800 with the 8 wire setup.
Turn Signal Wiring on The Jeep CJ3B Page

 

[quote=john fin;6858241Would this third option work?......bypass the parking light circuit to the front parking light bulbs and just use them as turn signals. Keep the single filament bulbs.[/quote]

Yeah, that would work but back then extra lights on your truck was just way cool... Kinda like zap straps and suicide *****. Go Figure... You had to be there...

Later Man...