As someone said, that dash switch does not cause the rear headrests to rise up into an upright position. Also rrgrassi, there are no motors related to the rear headrests.

With the engine running (and creating vacuum), pressing the dash button lets vacuum in to vacuum actuators, which unlock the rear headrests in an upright position. Gravity then causes the head rests to thump down.

To raise the headrests, one uses ones hands to lift them back to the upright locked position.

Do not try to push the headrests down without holding the dash switch.