The Sunbeam’s turn signals have been working since last summer. Push the stalk up and the right signals light up; push it down and the left ones flash. Initially the rear lights were very dim, so I converted the car to LEDs. That conversion, plus improving the ground wiring, made the lights much brighter and therefore safer. I even replaced the dashboard bulb that illuminates when the turn signal is on.
But the turn signals would not self cancel. In other words, after a turn was completed and the steering wheel returned to the center, the signal would not shut off. Most cars do this automatically, and the Sunbeam should it as well. 
I tried several times to address the problem but only recently have I seen success.
After some time staring at the mechanism I figured out how it works. On the right you can see the dashboard and steering column with the trim removed and the turn signal switch exposed. At the bottom of the picture is the turn signal lever or stalk. The electrical switch that passes power to the signals is on the bottom and cannot be seen. The white plastic piece near the center of the picture is the main part of cancellation mechanism. In this picture, the turn signal is off and the steering wheel is positioned straight ahead.
In the second picture, the car is turning 
right and the signal is in position to indicate a right turn. (Of course, the car is not moving. The front wheels are jacked up so that I can easily turn the steering wheel to simulate turns.) How can I tell? First, the white plastic cam has moved to the right and is now close to the steering column. Second, the thin steel strip that is bent into a hood shape is to the right of the white cam. In the first picture, it is below the cam.
How does the cancel mechanism work? F
irst, the driver pushes the stalk up or down to activate the indicator. She then turns the wheel and the hook slips under the white cam. When the driver returns the steering wheel to the center position, the hook pushes against the cam causing the indicator stalk to move back to the center or neutral position.
To the right is a picture of hook mentioned above out of the car for inspection. It turns out that hook needs to slide under the white cam when the turn is initiated but then make contact with it when the turn is completed and the steering wheel is re centered. I had trouble adjusting the bends for both of these functions.
Sunbeam 