Story & Photos By Jim Clark (The Hot Rod MD)

The turn signals on a vehicle are four separate lights that serve three different functions.  The first function directs power to the left front and left rear light to signal the intent to turn that way.  The opposite pair is energized to indicate a right turn.  A flasher in the power supply wire cycles on and off to create the flashing light effect.

The second function served by these lights is the flashing of all four lights indicating that the vehicle is experiencing some kind of emergency situation.  A separate flasher in the power supply to the emergency flasher switch causes the lights to flash when energized.  The third function is illuminating of the two rear lights to indicate that the vehicle is stopping.  A switch activated by hydraulic pressure or mechanically by the motion of the brake pedal sends power to the rear lights.

The three functions are performed by separate systems with their own activating switches but use the same four wires to the four individual lights.  The challenge when wiring the vehicle is to keep the power sent to one application from feeding back through the merging of the wire or switch connections, lighting filaments that you don’t want lit.

If your vehicle has a stock steering column or one equipped with turn signal mechanisms then you simply follow the wiring diagrams making the connections to the turn signal connector and other switches.  However, if your vehicle is not originally equipped with turn signals or has a roadster column without turn signals then there are alternative systems that can be installed.

I have a Flaming River roadster column in my roadster and ordered it without turn signal mechanisms.  I still want the added safety benefits that turn signals offer so I looked for alternatives.  The easiest installation that I found was the old accessory-style clamp-on turn signal assembly from Haywire in Joplin, MO.

Vintique Turn Signal Switch

This turn signal switch from Haywire in Joplin, MO is designed to clamp to the steering column.  The turn signal switch also includes the hazard switch.  Chrome housing features built in indicator lights and comes with easy to follow instructions.

The clamp-on works well in something like an early pickup truck but looks a little out of place on a hot rod that I was trying to keep clean and simple in its design.  Instead I chose to use a special-application toggle switch designed to function as a turn signal activator and brake light distribution point.

Turn Signal Toggle Switch

Simple toggle switch from Haywire in Joplin, MO incorporates the brake circuit and comes with turn signal flasher connector.  Power (12-V from the on side of the ignition switch) fed through a fuse and sent through the flasher in this connector ends up at the power-in pole on the toggle switch. 

My vehicle has a GM style fuse block with the flasher circuit included so I just ran power (purple wire) to pin number-1.  Most of the wiring kits use the GM color code for wires because they stayed the same over the years, while Ford and Mopar made changes from time-to-time.  The other wires hook-up to the poles as indicated: Green RR to Number-2, Blue RF Number-4, Light Blue LF Number-6, Yellow LR Number-8 and White from brake light switch to Number-7.  The switch ties the two rear filaments together; applying the brakes closes the circuit on the brake light switch energizing the lights.

I made a simple panel for the switches because I wanted to keep the dash as clean as possible.  Toggle switch at the left is the on-off-on multi-pole turn signal switch shown in the previous photos.  Center toggle is for controlling the Buick switch-pitch Turbo 400 transmission functions and the push-button switch at the right is for activating the horn.

This rear view of the switch panel shows how the various wires are connected via the screw-connections or push-on terminals on the turn signal switch.  Turn signal switch is rotated in the panel to allow the toggle to be flipped left-or-right depending on which direction you intend to turn.

The emergency flashers are a separate system and need a switch to activate them.  A simple toggle switch SPST (single-pole single-throw on-off) or similar pushbutton switch can be used but a diode will have to be installed in each individual wire going to each light.  The diodes are needed to prevent current from flowing backwards into other wires that are joined together, going to lamps that you don’t want lit during turn signal activation.  Diodes are available from Haywire but I chose to use this toggle switch FPST (four-pole single-throw on-off) toggle that keeps the four wires separated when the switch is in the off position.

This toggle switch that I chose for the emergency flashers has four separate terminals for power in and four separate terminals going out to each light.  They are not something in stock at most auto parts stores but I finally located one from Del City in Michigan.  It is listed as an obsolete part (#7920005) and may not be available in the future.  Carling makes a similar switch but it was quite pricey and could only be bought in quantity.  If you contact Haywire they may be able to supply one.

Power (12-V always-hot from the battery) through the fuse on the GM fuse panel and emergency flasher goes to the switch activating the flashing of the four turn signal filaments at once.  One wire in (Brown) is jumpered to tie the four terminals together as one.

Separate poles with an outgoing wire for each light send power to all filaments when the switch circuit is closed.

Wires from the emergency flasher switch are joined together with those at the turn signal switch terminals.  This allows both systems to function without any feedback because they remain separated until the emergency flasher switch circuit is closed.

Emergency flashers are not something that gets used routinely while driving so the switch can be mounted anywhere that is convenient.  I wanted to keep the dash in my roadster as uncluttered as possible so I mounted the emergency flasher switch into the steering column support beneath the dash.  It is still easily accessible but out of sight from above.

Self-Canceling Turn Signal

This self-canceling turn signal system from Haywire in Joplin, MO is programmable and easy to install: comes with two toggle switches, one for hazard, and one for turn signals.  This system incorporates the brake circuit and will not cancel the turn signal when the brakes have been applied.

The self-canceling turn signals offer the same type of activating device, a three-pole toggle switch (except that it is an (on)-off-(on) parentheses indicating momentary position) in place of the column-mounted lever and switch, but use electronics to make them cancel after a timed interval.  The momentary three-pole toggle switch activates the flashing sequence, which then cancels after a pre-set interval.  A small push-button micro switch ( (on)-off momentary) included as part of the assembly can be pushed to cancel the flashing at any time.

All of the electronic circuitry that makes the system function is contained within this small module that mounts under the dash near the fuse panel.  Small holes on the front of the panel are access holes for adjusting the duration of the flashing before it cancels.

This smorgasbord of electronic components combine to handle the incoming and outgoing signals from components via wires connected to the large connector and the small connector that routes from the three-pole (on)-off-(on) momentary toggle switch.

Instructions included with the system show where each wire is to connect to in the large connector and the small toggle switch connector.

Detailed diagram shows the source and connection points for everything in the self-canceling system.  The momentary push-button alternate-canceling switch connects to the hot side of the ignition-on terminal at the ignition switch and through the large connector to the electronics in the control box.  The emergency flasher toggle switch (supplied with the kit) receives always-hot power from the battery through a fuse and sends it through the emergency flasher to the control box.  All of the turn signal and emergency flasher functions are controlled by the electronics in the control box.

Rear shot of the control box shows the supplied double-stick tape used to mount it.  Small holes visible at the bottom and matching holes covered by the tape at the top are accessible from inside the box should you choose to mount the box with screws or bolts instead of the double-stick tape.

Summary

Four separate lights, located at the front and rear of the vehicle, serve as turn signals, emergency flashers and the two-rears as brake lights.  They may be included in the same housing or even in the same bulb, like the dual filament 1157–type, but they operate separately.  If your vehicle came equipped with these, or you are using a steering column so equipped, then you just attach the wires to the correct points as indicated by the manual or wiring diagram.

If you have an older vehicle not originally equipped with a turn signal system one can be added while retaining the original column.  A special multi-pole toggle switch, plus emergency flasher and brake light switch equipped with the necessary flashers and lights can substitute for the factory style system.  An alternative to the basic system is also available that uses modern electronics to perform all of the functions of an OEM system.

In either case it is important to equip a vehicle with a functional turn signal system for the safety of yourself and those that you share the road with.