the cancelling spring is a long coil spring that wraps around the steering shaft with each end attaching to the inner end of the signal stalk. friction of the spring against the shaft rotates the spring which pulls the stalk in the correct direction to cancel when the steering wheel is returned towards center after the turn.
i lived with a non-canceling signal for years, and it wasn't a big deal since i am used to manually canceling signals on motorcycles. when i pulled mine all apart during restoration, i discovered that the spring had polished down the shaft so well over the years that there was not enough friction to operate the stalk. so i roughed up the shaft surface throughly with a coarse sandpaper. now it self cancels just fine. though it does make a faint "ZZZZZZZ" sound now whenever i turn the wheel
