How to stop head from going through stuff?

So I have a crouch script but for some reason whenever I go under something and then stand up my head goes through the object I am supposed to be standing under. Any help here would be amazing, also I am not using a rigidbody controller so anything that deals with that is probably out of the question. Thanks in advance, please help!

var crouchSpeed : float = 3;
var charController : CharacterController;
var Player : Transform;
    private  var charHeight : float;
    private  var pos : Vector3;

    function Start (){
        Player = transform;
        charController = GetComponent(CharacterController);
        charHeight = charController.height;


    function Update (){
         var h : float= charHeight;
        if (Input.GetKey(KeyCode.C))
            h = 1;//charHeight*.05f;    

         var lastHeight : float= charController.height;
        charController.height = Mathf.Lerp(charController.height, h, Time.deltaTime * 5);
        pos.x = Player.position.x;
        pos.z = Player.position.z;
        pos.y = Player.position.y + (charController.height - lastHeight) / 2;
        Player.position = pos;


Raycast upwards when you go to un-crouch. If there’s something there, stay down.