Ford made major changes to the rear sequential turn signal system on Thunderbirds during model year 1969 production, with the switch to a solid state transistorized sequencer unit. This improvement eliminated the motor and cam assembly, in use since its introduction in 1965, as well as the cumbersome relays that went with them. The result was an overall improved performance of the signaling system, from the driver's point of view, but out back where it really counted, the brake and turn signal lights were getting hard to see to the driver of the vehicle following behind. There are a couple of reasons for this.

In 1966, the Thunderbird's brake and turn lamps were so bright they almost blinded the person following behind, causing some to ask how they ever got approved. For 1967, Ford changed the design of the tail lamps to eliminate the glare and create a unique glow effect that illuminated the lens indirectly. Under some conditions, however, these lights were difficult to see, even though they ran the full length of the rear of the car.

In order to comply with 1970 Federal Motor Vehicle Safety Standards, the sequential turn signal system was revised on December 29, 1970 to increase the brightness of the brake and signal lamps. This was accomplished through the addition of four relays to the solid state sequencer unit. Literally taped onto the black plastic housing of the sequencer unit, the relays are energized by, and work in combination with, the transistorized sequencer unit, to illuminate the center and outboard bulbs, reducing the load on the transistors inside the black box. A special flasher was used to compensate for the difference in current load the relays created.

The result was brake and turn signal lamps that were brighter, thus easier to see and safer than they were before, while meeting the standards required by law. The updated parts may be used on cars built prior to this change, as the wiring connections are identical. However, it is important to change the flasher units located in clips on both sides of the glove compartment box for proper operation.



Now you know!

Updated part numbers:
Sequencer and Relay Assembly D0WY-13A366-A
Turn Signal Flasher D0WY-13350-C
Emergency Warning Flasher D0WY-13350-A

Articles of interest:
Automotive Brake Light Bulb Comparison
Sequential Turn Signals | AUTO BREVITY