First Person Camera disabling

I am using the built in 1st person controller and am trying to script for a camera change from the player camera to a world map camera, using this script:

var camera1 : Camera; 
var camera2 : Camera; 

function Start () { 
    camera1.enabled = true; 
    camera2.enabled = false; 
} 

function Update () { 
    if (Input.GetKeyDown ("2")){ 
        camera1.enabled = false; 
        camera2.enabled = true; 
    } 
    if (Input.GetKeyDown ("1")){ 
        camera1.enabled = true; 
        camera2.enabled = false; 
    }     
}

This is not working however. I am getting the world map view, but it does not change back to the player camera when I click the button again. I think it is because the first person camera is not disabling, but I am not sure. Please help.

That was the original, sorry, the one I used was this:

var camera1 : Camera; 
var camera2 : Camera; 

function Start () { 
    camera1.enabled = true; 
    camera2.enabled = false; 
} 

function OnMouseUp () { 
    if (camera1.enabled == true){ 
        camera1.enabled = false; 
        camera2.enabled = true; 
    } 
    if (camera2.enabled == true){ 
        camera1.enabled = true; 
        camera2.enabled = false; 
    }     
}