Use a utility knife to "V" cut the crack slightly. Be careful not to cut too much, shave away just enough to form a "V" shape, to allow easy application of the silicone caulking.
Clean well both inside and outside of the crack, removing all dust and loose particles. Allow the area to dry well before proceeding.
Mask either side of the crack with painters tape to keep the caulking in the opening and not on the good vinyl dashboard. Silicone caulking dries clear, but shiny.
Apply the silicone caulking into the crack and allow it to dry for 10 to 15 minutes, before removing the tape. If the crack is small, simply remove the tape and allow the silicone to dry. If the crack is larger, you can choose to texture the silicone using the texturizing portion of a vinyl repair kit. It is best to texture before removing the tape, however you must texture within 10 to 15 minutes, before the silicone dries too much to take the texture.
Paint larger cracks in your dashboard with motor car vinyl paint to reduce visibility. Allow the silicone to dry at least two hours before painting