variable switching...

This is my script for switching a variable to produce an Ikaruga type effect for my game. Different things happen depending on what value (only 1 or 2) "MOD" is set to. In the code, if I set MOD to two, play the scene and then press Fire1, MOD goes to 1. But, if I press fire again, it wont switch back to 2, and if I set MOD to 1 in the code, it will not switch to two. What is wrong? Thanks

function Update (){
    if( (Input.GetButtonDown( "Fire1")) && (MOD==1)){MOD=2;}
    if( (Input.GetButtonDown( "Fire1")) && (MOD==2)){MOD=1;}        
}

Add else before the second if. It's hitting the first one, setting MOD to 2, then going into the second if and setting it back to 1