var pointerr = 0;

Text = new Array ("text1", "text1", "text1", "text1", "text1", "text1");

timer();

function textwechsel() { 
document.getElementById("textwechsel").src = preesrc + Text[pointerr];
if (pointerN == (Text.length-1)) { pointerr = 0;}
else { pointerr++; }
timer();
}

function timer() {
window.setTimeout("textwechsel()", 5000);  // 5000 milisekunden bis wechsel
}