Place the potatoes in a bowl of cold water for at least 30 minutes to remove excess starch.
Drain the potatoes and pat the potatoes dry.
Lightly spray the air fryer basket and put the potatoes inside. Either spray the potatoes again with oil or lightly pour some oil (about a tablespoon) into the air fryer basket. Stir the contents around to evenly distribute the oil onto the potatoes. Season the potatoes with the ranch seasoning and stir the contents to distribute the seasoning.
Lightly spray the potatoes one more time and cook at 380°F/193°C for 10-15 minutes, stirring at the halfway point. Test the potatoes with a fork once they are done cooking. If the potatoes need more time and an additional minute or two at 400°F/204°C.