Footsteps script not working

I want a footsteps script with stamina. I have already implemented the sound but cannot implement the stamina. If anybody could modify the code or tell me how to do this, I would be very greatful. Here is what I have done so far:

 #pragma strict
 @script RequireComponent( AudioSource )
  
 var walk : AudioClip;
 var run : AudioClip;
 var water : AudioClip;
  
 var walkAudioSpeed : float = 0.4;
 var runAudioSpeed : float = 0.2;
  
 private var walkAudioTimer : float = 0.0;
 private var runAudioTimer : float = 0.0;
  
 @HideInInspector
 var isWalking : boolean = false;
 @HideInInspector
 var isRunning : boolean = false;
  
 var walkSpeed: float = 7; // regular speed
 var runSpeed: float = 20; // run speed
 
 @HideInInspector
 var inWater : boolean = false;
 
 private var chCtrl: CharacterController;
 private var chMotor: CharacterMotor;
 
 //Stamina Vars
 private var maxStamina : float = 100.0;
 private var ranOut : boolean = false;
 var Stamina : float = 100.0;
 var staminaRespawnRate : float = 5.5;
 
 function Start()
 {
     chCtrl = GetComponent(CharacterController);
     chMotor = GetComponent(CharacterMotor);
 }
  
 function Update()
 {
     SetSpeed();
  
     if ( chCtrl.isGrounded )
     {
         PlayFootsteps();
     }
     else
     {
         walkAudioTimer = 0.0;
         runAudioTimer = 0.0;
     }
 }
  
 function SetSpeed()
 {
     //Normal health regeneration
     if(Stamina < 100)
     {
         Stamina += Time.deltaTime * staminaRespawnRate;
     }
     
     //When health reaches 100, set to maxHealth
     if(Stamina > maxStamina)
     {
         Stamina = maxStamina;
     }
     var speed = walkSpeed;
     if (Stamina > 0)
     {
         if ( chCtrl.isGrounded && Input.GetKey("left shift") || Input.GetKey("right shift") )
         {
             speed = runSpeed;
         }
      
         chMotor.movement.maxForwardSpeed = speed;
     }
     else if (Stamina <= 0)
     {
         //Stamina = 0;
         ranOut = true;
         speed = walkSpeed;
         chMotor.movement.maxForwardSpeed = speed;
         isWalking = true;
         isRunning = false;
     }
     if (Stamina <= 25)
     {
         ranOut = false;
     }
     
 }
  
 function PlayFootsteps() 
 {
     if ( Input.GetAxis( "Horizontal" ) || Input.GetAxis( "Vertical" ) )
     {
        if ( Input.GetKey( "left shift" ) || Input.GetKey( "right shift" ) )
        {
             if (Stamina > 1 && ranOut == false)
             {    
                  // Running
                  isWalking = false;
                  
                  Stamina -= 1;
                  isRunning = true;
             }
             else
             {
                 // Walking
                  isWalking = true;
                  isRunning = false;
             }
         }
        else
        {
          // Walking
          isWalking = true;
          isRunning = false;
        }
     }
     else
     {
        // Stopped
        isWalking = false;
        isRunning = false;
     }
  
     // Play Audio
     if ( isWalking && inWater)
     {
        if ( audio.clip != water )
        {
          audio.Stop();
          audio.clip = water;
        }
  
        //if ( !audio.isPlaying )
        if ( walkAudioTimer > walkAudioSpeed )
        {
          audio.Stop();
          audio.Play();
          walkAudioTimer = 0.0;
        }
     }
     else if ( isWalking )
     {
        if ( audio.clip != walk )
        {
          audio.Stop();
          audio.clip = walk;
        }
  
        //if ( !audio.isPlaying )
        if ( walkAudioTimer > walkAudioSpeed )
        {
          audio.Stop();
          audio.Play();
          walkAudioTimer = 0.0;
        }
     }
     else if ( isRunning && inWater)
     {
        if ( audio.clip != water )
        {
          audio.Stop();
          audio.clip = water;
        }
  
        //if ( !audio.isPlaying )
        if ( runAudioTimer > runAudioSpeed )
        {
          audio.Stop();
          audio.Play();
          runAudioTimer = 0.0;
        }
     }
     else if ( isRunning )
     {
        if ( audio.clip != run )
        {
          audio.Stop();
          audio.clip = run;
        }
  
        //if ( !audio.isPlaying )
        if ( runAudioTimer > runAudioSpeed )
        {
          audio.Stop();
          audio.Play();
          runAudioTimer = 0.0;
        }
     }
     else
     {
        audio.Stop();
     }
  
     // increment timers
     walkAudioTimer += Time.deltaTime;
     runAudioTimer += Time.deltaTime;    
 }

Thanks,

Stormy102