sequential turn signals

Sequential turn signals are a feature on some cars whereby the lights that form the rear turn signal don't follow the simple pattern of on then off, repeating, but instead perform a more complicated sequence. This is obviously much easier to do on an American car because of the common usage of the same red tail lights as both brake lights and turn signals; there is therefore much more room to play with than the European and Japanese usage of separate yellow turn signals and red brake lights.

The most common sequence employed requires three red lights per side that can be used as turn signals. The innermost light is lit first, followed by the middle light being lit, then the outermost. All are on for a brief moment, then all turn off and the cycle is repeated, giving a kind of strobing, directional effect. The ASCII art below might serve to illustrate this better than words: here, the boxes filled with Xes signify lights turned on.

__________________                __________________                __________________                __________________
_________________ \               _________________ \               _________________ \               _________________ \            
                 \ \                               \ \                               \ \                               \ \              
                  \ \                               \ \                               \ \                               \ \             
                   \ \                               \ \                               \ \                               \ \            
                    \ \                               \ \                               \ \                               \ \           
_____________________\_\__        _____________________\_\__        _____________________\_\__        _____________________\_\__        
                          \                                 \                                 \                                 \       
                          |                                 |                                 |                                 |       
   ---------------------- |          ---------------------- |          ---------------------- |          ---------------------- |       
   |      |      |      | |          |XXXXXX|      |      | |          |XXXXXX|XXXXXX|      | |          |XXXXXX|XXXXXX|XXXXXX| |       
   |      |      |      | |          |XXXXXX|      |      | |          |XXXXXX|XXXXXX|      | |          |XXXXXX|XXXXXX|XXXXXX| |       
   |      |      |      | |          |XXXXXX|      |      | |          |XXXXXX|XXXXXX|      | |          |XXXXXX|XXXXXX|XXXXXX| |       
   ---------------------- |          ---------------------- |          ---------------------- |          ---------------------- |       
                          |                                 |                                 |                                 |       
                          |                                 |                                 |                                 |       
                          /                                 /                                 /                                 /       
_________________________/        _________________________/        _________________________/        _________________________/        
               |       |                         |       |                         |       |                         |       |          
               |       |                         |       |                         |       |                         |       |          
               \_______/                         \_______/                         \_______/                         \_______/          
================================  ================================  ================================  ================================  

Sequential turn signals were factory fitted to Ford Thunderbirds built between 1965 and 1971, inclusive, to Mercury Cougars between 1967 and 1973, to Shelby Mustangs between 1968 and 1970, and to 1969 Chrysler Imperials. No other production cars were so fitted, as far as I know; this may have been due to worries about the system's complexity, and to automotive fashion.

Two different systems were employed. The earlier, fitted to the 1965 through 1968 cars, was electro-mechanical, featuring an electric motor driving, through reduction gearing, a set of three slow-turning cams. These cams would actuate switches to turn on the lights in sequence so long as the turn signal switch was set. This system was complicated and prone to failure, and therefore it's rare to find one of these cars with an original and still fuctioning unit these days. The part is long out of stock at Ford and it is practically impossible to find a NOS unit. The odds of finding a working one second-hand are slim, too. Fortunately, someone has built an electronic replacement unit, if you don't care about total authenticity - if you do, you're on your own repairing an original one.

Later cars used a transistorized 'black box' with no moving parts; this was much more reliable. You can find the sequential unit in the trunk on Cougars and Thunderbirds, affixed behind the back seat, in all model years that had them.

I believe the 1969 Chrysler Imperial also used a transistorized unit.

If you want to fit sequential turn signal lights to a car that didn't originally have them, you're in luck - provided you can find three lights per side that you can make sequential, at least! Quite a few cars are so equipped. Electronic sequential flasher units are available from a number of companies, with instructions on how to retrofit them to a variety of cars. The most commonly done are late-model Ford Mustangs, Chevrolet Impalas, Pontiac Firebirds and Chevrolet Camaros, but the kits are adaptable.

Sequential turn signals are legal in all states of the USA (and I believe Canada); I do not have information as to their legality elsewhere. Sequential brake lights (where the same circuit is used for when the brake lights come on) are definitely illlegal in several states, including I believe New Jersey and Florida. It's possible that sequential emergency flashers are not legal in some jurisdictions either.

In summary, sequential turn signals are a neat feature on a car, particularly one that had them from the manufacturer - if they work. If they don't, and keeping them working is much more complicated than for a regular system, they're very annoying indeed. The sequential lights in my 1967 Ford Thunderbird don't work right now, and I'm probably going to have to buy an electronic replacement unit (almost $200) and do a lot of electrical work before they do. This is pretty typical of even a well-maintained car from this era.