Camera switch after specific time

I have tryed making a code, that makes the scene start at one camera(third person) and then after a specific time it switches to another camera(first person). The only problem is, that it doesn't show any errors but the code won't work, it doesn't switch camera.

Can anyone tell me what is wrong?

Here is the code

 var camera1:Camera;
 var MainCamera:Camera;
 
 function Start () {
 
 camera1.enabled = true;
 MainCamera.enabled = false;
 
 }
 
 function Switch(){
 
 if (camera1.enabled == true) {
     
     yield WaitForSeconds(1.0);
     camera1.enabled = false;
     MainCamera.enabled = true;
     }
     
 }