OnCheckedChange doesnt fire server side

I know there is many questions about this and i have looked at the answers but nothing works for me when i test the answers they got.

My problem is that i can´t reach the method on server side when the checkbox is checked or unchecked. Nothing happens.

Here is my code:

The repeater:

<asp:Repeater ID="rptTimeWeekTable" OnItemDataBound="rptrptTimeWeekTable_ItemDataBound" OnItemCommand="rptTimeWeekTable_ItemCommand" runat="server">

The checkbox:

<asp:CheckBox ID="chBoxSum" runat="server" Enabled="true" OnCheckedChanged="chBoxSum_CheckedChanged" AutoPostBack="true"></asp:CheckBox>

Code behind:

protected void chBoxSum_CheckedChanged(object sender, EventArgs e)
{
    CheckBox chBox = (CheckBox)sender;

    int rowIndex = ((RepeaterItem)chBox.NamingContainer).ItemIndex;

    CheckBox chBoxMon = rptTimeWeekTable.Items[rowIndex].FindControl("chBoxMonday") as CheckBox;
    CheckBox chBoxTue = rptTimeWeekTable.Items[rowIndex].FindControl("chBoxTuesday") as CheckBox;
    CheckBox chBoxWed = rptTimeWeekTable.Items[rowIndex].FindControl("chBoxWednesday") as CheckBox;
    CheckBox chBoxThu = rptTimeWeekTable.Items[rowIndex].FindControl("chBoxThursday") as CheckBox;
    CheckBox chBoxFri = rptTimeWeekTable.Items[rowIndex].FindControl("chBoxFriday") as CheckBox;
    CheckBox chBoxSat = rptTimeWeekTable.Items[rowIndex].FindControl("chBoxSaturday") as CheckBox;
    CheckBox chBoxSun = rptTimeWeekTable.Items[rowIndex].FindControl("chBoxSunday") as CheckBox;

    if (chBox.Checked == true)
    {
        chBoxMon.Checked = true;
        chBoxTue.Checked = true;
        chBoxWed.Checked = true;
        chBoxThu.Checked = true;
        chBoxFri.Checked = true;
        chBoxSat.Checked = true;
        chBoxSun.Checked = true;
    }
    else
    {
        chBoxMon.Checked = false;
        chBoxTue.Checked = false;
        chBoxWed.Checked = false;
        chBoxThu.Checked = false;
        chBoxFri.Checked = false;
        chBoxSat.Checked = false;
        chBoxSun.Checked = false;
    }

}

    protected void rptTimeWeekTable_ItemCommand(object source, RepeaterCommandEventArgs e)
{

}

Hope you guys can help me.