Timer - CS0029: Cannot implicitly convert type `float' to `bool'

I'm getting this error when trying to setup my timer (Assets/Scripts/ShroomScript.cs(47,25): error CS0029: Cannot implicitly convert type float' to bool')

 using UnityEngine;
 using System.Collections;
 
 public class ShroomScript : MonoBehaviour {
 
     private heroController player;
     public float timeLeft = 60f;
 
 
 
 
     // Use this for initialization
     void Start () {
 
         player = GameObject.FindGameObjectWithTag("Player").GetComponent<heroController>();
 
     
     }
     
     void OnTriggerEnter2D(Collider2D col) {
 
         if(col.CompareTag("Player")){
 
             AudioSource AS = col.GetComponent<AudioSource>();
             AS.PlayOneShot(AS.clip);
             Destroy(gameObject);
             if (player.curHealth <=4)
             {
                 player.HealthIncrease(1);
             }    else if (player.curHealth >= 5) 
             {
                 player.HealthIncrease(0);
             }
             player.shroomPower = true; 
 //            timeLeft = 5;
                 
         }
 
 
             
 }
     void Update ()     {
         if(timeLeft > 0)
         {
             Debug.Log("Waiting"+timeLeft);
             timeLeft -= Time.deltaTime;
             if (timeLeft = 0)        
             {player.shroomPower = false;}
 
         }
 
     }
 
             
 }