It flashes like a strobe. I would manually manipulate the switch on and off. 1939 trucks used the same parking/turn signal light on the front fender as the passenger cars. Looked like something out of star wars. 1940 trucks they were much smaller. I couldn't bring myself to drill holes in the top of my nos fenders to mount them, so I used 1939 Chevrolet fog lights instead. I'll see if there is a part number on the flasher unit. There was no return to neutral position, off, after turning back then. You have to remember to return it to the off position.
Rick
