using UnityEngine;
using System.Collections;

public class BLight : MonoBehaviour {
    public Light Test;
    public bool TTT;

void Update () {
  if (Input.GetKey (KeyCode.T)) {
   TTT = !TTT;
}
    StartCoroutine(Test4());    
    }
    IEnumerator Test4(){
  if (TTT) {
   while (true) {
       yield return new WaitForSeconds (1f);
       Test.enabled = false;
       yield return new WaitForSeconds (1f);
       Test.enabled = true;
   }
}
}
}

using UnityEngine;
using System.Collections;

public class BLight : MonoBehaviour
{
    public Light Test;
    public bool isRunning;

    void Update()
    {
        if (Input.GetKeyDown(KeyCode.T))
        {
            isRunning = !isRunning;
            if (isRunning)
            {
                StartCoroutine(Test4());
            }
        }
    }

    IEnumerator Test4()
    {
        while (true)
        {
            yield return new WaitForSeconds(1f);
            if (!isRunning)
                break;
            Test.enabled = !Test.enabled;
        }
    }
}

using UnityEngine;
using System.Collections;

public class BLight : MonoBehaviour
{
    public Light Test;
    public bool isRunning;
    private Coroutine current;

    void Update()
    {
        if (Input.GetKeyDown(KeyCode.T))
        {
            isRunning = !isRunning;
            if (isRunning)
            {
                current = StartCoroutine(Test4());
            }
            else if (current != null)
            {
                StopCoroutine(current);
            }
        }
    }

    IEnumerator Test4()
    {
        while (true)
        {
            yield return new WaitForSeconds(1f);
            Test.enabled = !Test.enabled;
        }
    }
}