L1A7

I have been haunted for many years now with an occasional stray full cycle single swipe of the wipers with the control in the OFF position. My '79 C-10 pickup has a tilt steering wheel but the stray happens out of the blue, not when I hit a pot hole or speed bump, which might indicate a short. My NAPA guy said its a short in the steering column and my mechanic buddy said I have a leaky capacitor. I can't find a capacitor on the wiring diagram and I don't want to take the steering column apart unless I must. The wiper switch with delay was replaced with no effect. Other than that, the wipers work flawlessly. Any constructive advise?