Displaying accented character in Javascript

Question

I am having problem displaying accented character in my app; It is showing ⛽ instead of ó. The string is coming from a json file retrieved from a server. Here are the technical details:

JSON: (This is the object being retrieved from the server)
notice the 3rd key "Relación" the letter "o" is accented.

[
    {
        "key": "Canales"
    },
    {
        "key": "Productos"
    },
    {
        "key": "Relación con el ejecutivo"      
    }
]

Ajax (here is the code to retrieve the information)
notice I already added charset=utf-8 as most answers suggest

$.ajax({
    url: url,
    type: "GET",
    dataType: "json",
    contentType: "application/json; charset=utf-8",
    success: function(uri){
         alert("clintg test: " + JSON.stringify(uri));
    }
}

Alert: (as you can see, it is just showing a box symbol where it's supposed to be -> ó)

Answer 1

To give more detail to @georg 's advice that helped me solve this issue:

Since I can't change the server side scripts, I adjusted the code on my side.
I changed the charset in my ajax request to ISO-8859-1, but since the default charset of ajax is utf-8, I had to override the charset with $.ajax.beforeSend:

$.ajax({
    url: url,
    type: "GET",
    dataType: "json",
    contentType: "application/json; charset=iso-8859-1",
    success: function(uri){
         alert("clintg test: " + JSON.stringify(uri));
    },
    beforeSend: function(jqXHR) {
        jqXHR.overrideMimeType('application/json;charset=iso-8859-1');
    }
}

Here's a link to the question that helped me figure out and override the charset: Jquery ignores encoding ISO-8859-1