Unity Build&RunをするとGetKeyDownが反応しません

 前提・実現したいこと

c#でspaceキーを押すと3Dモデルの髪の色が変わるものを作りたいと思っています。
乱数で髪の色を変えているので、その乱数をcsvファイルに出力しています。

 発生している問題・エラーメッセージ

下記のコードでは、プレイモードでは動くのですが、Build&Runをするとキーが反応してくれません。
csvファイルの方もBuild&RunではStart()の分しか出力されていません。
プレイモードの方ではキーの回数に合わせて出力もできています。
何か解決方法を教えて頂けないでしょうか

 該当のソースコード

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.IO;
using System;

public class haircolor2 : MonoBehaviour {


    public Texture hair001;
    public Texture hair002;
    public Texture hair003;
    public Texture hair004;
    public Texture hair005;
    public Texture hair006;
    public Texture hair007;
    public Texture hair008;
    public Texture hair009;
    public Texture hair010;
    public Texture hair011;
    public Texture hair012;
    public Texture hair013;
    public Texture hair014;
    public Texture hair015;
    public Texture hair016;
    public int count;
    // Use this for initialization
    void Start () {
        Renderer render = GetComponent<Renderer>();
        count = 1;
        int h = UnityEngine.Random.Range(1, 17);
        hair2Save(h);
        switch (h)
        {
            case 1:
                render.material.mainTexture = hair001;
                break;
            case 2:
                render.material.mainTexture = hair002;
                break;
            case 3:
                render.material.mainTexture = hair003;
                break;
            case 4:
                render.material.mainTexture = hair004;
                break;
            case 5:
                render.material.mainTexture = hair005;
                break;
            case 6:
                render.material.mainTexture = hair006;
                break;
            case 7:
                render.material.mainTexture = hair007;
                break;
            case 8:
                render.material.mainTexture = hair008;
                break;
            case 9:
                render.material.mainTexture = hair009;
                break;
            case 10:
                render.material.mainTexture = hair010;
                break;
            case 11:
                render.material.mainTexture = hair011;
                break;
            case 12:
                render.material.mainTexture = hair012;
                break;
            case 13:
                render.material.mainTexture = hair013;
                break;
            case 14:
                render.material.mainTexture = hair014;
                break;
            case 15:
                render.material.mainTexture = hair015;
                break;
            case 16:
                render.material.mainTexture = hair016;
                break;
            default:
                render.material.mainTexture = hair001;
                break;
        }

    }

    void Update () {
          Renderer render = GetComponent<Renderer>();

          if (Input.GetKeyDown(KeyCode.Space))
        {
            count++;
            int h = UnityEngine.Random.Range(1, 17);
            hair2Save(h);

            switch (h)
            {
                case 1:
                    render.material.mainTexture = hair001;
                    break;
                case 2:
                    render.material.mainTexture = hair002;
                    break;
                case 3:
                    render.material.mainTexture = hair003;
                    break;
                case 4:
                    render.material.mainTexture = hair004;
                    break;
                case 5:
                    render.material.mainTexture = hair005;
                    break;
                case 6:
                    render.material.mainTexture = hair006;
                    break;
                case 7:
                    render.material.mainTexture = hair007;
                    break;
                case 8:
                    render.material.mainTexture = hair008;
                    break;
                case 9:
                    render.material.mainTexture = hair009;
                    break;
                case 10:
                    render.material.mainTexture = hair010;
                    break;
                case 11:
                    render.material.mainTexture = hair011;
                    break;
                case 12:
                    render.material.mainTexture = hair012;
                    break;
                case 13:
                    render.material.mainTexture = hair013;
                    break;
                case 14:
                    render.material.mainTexture = hair014;
                    break;
                case 15:
                    render.material.mainTexture = hair015;
                    break;
                case 16:
                    render.material.mainTexture = hair016;
                    break;
                default:
                    render.material.mainTexture = hair001;
                    break;
            }
        }
    }
    public void hair2Save(int h)
    {
        StreamWriter sw;
        FileInfo fi;
        fi = new FileInfo(Application.dataPath + "/logL/hair.csv");
        sw = fi.AppendText();
        sw.Write(count + ",");
        sw.WriteLine(h);
        sw.Flush();
        sw.Close();
    }
}

 試したこと

GetKeyでは動きますが、カウントが上手く出来ないのでGetKeyDownを使いたいです。

 補足情報（FW/ツールのバージョンなど）

Unity５　C#