If I create an instance in “function Start” and give it a texture like below it works:

function Start () {
    var instance : GameObject = Instantiate(Resources.Load("103")) as GameObject;
    instance.renderer.material.mainTexture = Resources.Load("entextur");
}

…But if I do the same thing in a “function Update” it doesnt. Like this:

function Update () {

if(Input.GetMouseButtonDown(0) && Input.mousePosition.y < 200){

 var instance : GameObject = Instantiate(Resources.Load("103")) as GameObject;
    instance.renderer.material.mainTexture = Resources.Load("entextur");
}
}

Why doesnt it work and how do I make it work?

Why aren’t you just keeping the texture in a variable and load it in the start function, but then use the variable in the update function to assign the material texture?