Add Turn Signals To An Old Car

Article by Mark Trotta

Besides being a requirement in most states, adding turn signals to an old car makes them better suited for today's roads and traffic. As an added bonus, you also get 4-way safety flashers.

Recently, I converted an old CJ Jeep from 6 volts to 12 volts, and in the process added turn signals. The procedure is about the same for any old car or truck.

The first step is figuring out where to mount the additional lights on your vehicle.

Although the Jeep CJ2A came equipped with front running lamps that could have been hooked up as signals, it was decided to add a pair of signal lamps under the front bumper.

The rear signals were incorporated into the existing stop/tail lamps.

Read: Restore An Old Jeep

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Signal Switch Mounting

The next step was mounting the T/S switch to the steering column.

To find the best location, put your hands on the steering wheel and reach with your left hand to feel where the best spot will be.

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Bad Instructions!

Nearly every turn signal switch made today is from overseas, which means the instructions were translated from a foreign language into English. Sometimes they're hard to understand, and sometimes they're just plain wrong. And it's common for one manufacturer to copy another manufacturer's instructions, leaving more room for errors and confusion.

Wiring A Turn Signal Switch

All you really need from the instruction sheet is the wiring diagram.

Most aftermarket turn signal switches, like the one I installed, have seven wires. The colors of the wires can vary. I've only listed them for reference.

7-Wire Turn Signal Switch

1) From fuse box to flasher socket (black)
2) From stoplight switch (red)
3) Ground (blue)
4) Left front (yellow)
5) Right front (green)
6) Left Rear (orange)
7) Right rear (brown)

Power starts from the fuse box, goes through an inline fuse, and into the flasher socket. I hooked up the switch to a "hot" lead, meaning it's on all the time even without the key. This was done so that the flashers could be operated without having to turn the key or start the motor.

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The auxiliary lamps mounted below the front bumper were two-wire units; one wire goes to the T/S switch, the other goes to a ground. The rear signal wires were spliced in with the brake lights.

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Flasher Function

When you push the turn-signal stalk up or down, a thermal flasher connects to the turn-signal bulbs through the turn-signal switch. This completes the circuit, allowing current to flow. When power is put into the flasher, the spring heats up the internal strip, then cools down, then heats up, in succession, until the stalk is moved back to the middle position.

Thermal Flasher vs Electronic Flasher

Although electronic flashers have been around since the 1970's, I prefer old-school thermal flashers, which contain a bi-metallic spring. Both work.

Conventional vs LED Lights

LED lights are brighter than conventional bulbs, and they also draw less current. Most of the time this is a good thing, but in some cases, it will affect the flashers "heat and cool" ability. The fix for this is to replace the conventional thermal flasher with a No Load LED flasher.

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If you've hooked everything up, and none of the lights come on, it's a power supply problem. Check the power coming into the flasher socket with a 12-volt Test Light.

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Universal Turn Signal Switch

Aftermarket units such as the 7-Wire Turn Signal Switch I installed on the Jeep have been around for decades.

Also available, but less popular, are 8-wire turn signal units. The extra wire would go to the front parking lamp terminal on the headlight switch. This would allow parking lamps to stay lit while the headlamp's are on. This may be a law in your state, so check before you purchase the switch.

Chrome Turn Signal Switch

For those looking for a chrome turn signal switch, you'll probably find them offered with a plastic housing. Here's one that will work with nearly every vintage car or truck, provided it is 12-volts.