transform.Rotate(Vector3.up ... not working

I'm trying to rotate my character on the y axis 180 degrees, so he faces the direction he is facing. Side scroller game. The character move just will not face the other direction.

Thank you in advance.

using UnityEngine; using System.Collections;

 public class CharacterMovement : MonoBehaviour {
 
     public float maxSpeed = 6.0f;
     public bool facingRight = false;
     public float moveDirection;
 
     // Use this for initialization
     void FixedUpdate () 
     {
         GetComponent<Rigidbody>().velocity = new Vector2 (moveDirection * maxSpeed, GetComponent<Rigidbody>().velocity.y);
 
         if (moveDirection > 0.0f && !facingRight)
         {
             Flip();
         }
         
         else if (moveDirection < 0.0f && !facingRight)
         {
             Flip();
         }
     }
     
     // Update is called once per frame
     void Update () 
     {
         moveDirection = Input.GetAxis ("Horizontal");
     }
 
     void Flip()
     {
         facingRight = !facingRight;
 
         transform.Rotate(Vector3.up, 180.0f, Space.World);
   }
 }