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