google maps api infowindow vários marcadores, mesmo local

var markerContents={};
  var infoWindow = new google.maps.InfoWindow;

downloadUrl("map/map_data_source.php", function(data) {

  var xml = data.responseXML;


  var markers = xml.documentElement.getElementsByTagName("marker");
  for (var i = 0; i < markers.length; i++) {

  var date = markers[i].getAttribute("date");
  var artist = markers[i].getAttribute("artist");
  var venue = markers[i].getAttribute("venue");
  var address = markers[i].getAttribute("address");
  var city = markers[i].getAttribute("city");
  var idgigs = markers[i].getAttribute("id");
  var country = markers[i].getAttribute("country");
  var count = markers[i].getAttribute("count");
  var swith = markers[i].getAttribute("swith");
  var stage = markers[i].getAttribute("stage");
  var type = markers[i].getAttribute("type");
  var point = new google.maps.LatLng(
      parseFloat(markers[i].getAttribute("lat")),
      parseFloat(markers[i].getAttribute("lng")));
  var customIcons = {
 FFFFFF: {
icon: 'http://chart.apis.google.com/chart?chst=d_map_pin_letter&chld=' + count + '|' + type + '|000000'
},
upcoming: {
icon: '../map/marker/orange.png'
 }
};
  var markerId = point.toString();
  if(!markerContents[markerId]){
  markerContents[markerId] = [];
  }

var html =
   '<div id="infoWindow" width="600px"><img src="projects/components/' + artist + '">' +
  '<br><br>' + date +
  '<br><b>' + venue + '</b> / ' + city + '<br>' + swith + stage +
  '<br><b><a class="second_sub_menu" href="../projects/bands.php?sub=Setlist&info=' + artist + '&id=' + idgigs + '">SHOW INFORMATION</a></b>';

  var icon = customIcons[type] || {};


markerContents[markerId].push(html);



    var marker = new google.maps.Marker({
    map: map,
    position: point,
            zIndex: i,
    icon: icon.icon
});




 bindInfoWindow(marker, map, infoWindow, markerContents[markerId]);

  }
  });
  }

function bindInfoWindow(marker, map, infoWindow, html) {
google.maps.event.addListener(marker, 'click', function() {
infoWindow.setContent(html.join('<hr/>'));
infoWindow.open(map, marker);

 if (map.getZoom() < 4) map.setCenter(marker.getPosition());
 if (map.getZoom() < 4) map.setZoom(4); 
 });
 google.maps.event.addListener(map, "click", function() {infoWindow.close();});
 }