Removing jQuery Validation on the fly

I'm trying to prevent the jQuery Validation plugin from validating if a certain form option (phone only) is selected using $("#form_id").rules("remove", "required"); feature, but it's not working...

All I get is a javascript error when I select phone only: "TypeError: Result of expression 'F' [undefined] is not an object, and the form won't submit since it's still validating required fields.

//field validation
$('#location').change(function(){
    location_val = $('#location').val();

    if (location_val == "select") {
        $('.hide').hide();
    }
    else if (location_val == "my_location") {
        $('.hide').hide();
        $('#f_address, #f_address2, #f_city, #f_state_zip, #f_phone').customFadeIn('fast');
        $("#step2").rules("add", "required");
    }
    else if (location_val == "customers_location"开发者_运维百科) {
        $('.hide').hide();
        $('#f_area, #f_phone, #f_city, #f_state_zip').customFadeIn('fast');
        $("#step2").rules("add", "required");
    }
    else if (location_val == "both") {
        $('.hide').hide();
        $('#f_area, #f_address, #f_address2, #f_city, #f_state_zip, #f_phone').customFadeIn('fast');
        $("#step2").rules("add", "required");
    }
    else if (location_val == "phone") {
        $('.hide').hide();
        $('#f_phone').customFadeIn('fast'); 
        $("#step2").rules("remove", "required");

    }
});

$("#step2").validate({
    rules: {
        city: {required: true},
        state: {required: true},
        zip: {required: true}
    }
});

Insights appreciated.

The way I accomplished this task is to use a CSS class that is different from the Validation ruleset. So for fields that are normally 'required' I am generating the elements with a 'requirement' CSS class. Then I add this in the page:

function addRequired() {
    $('.requirement').each(function() {
        $(this).rules("add", {required: true});
    });
}

function removeRequired() {
    $('.requirement').valid(); // can't remember why I have this, but it's in source control now for awhile...
    $('.requirement').each(function() {
        $(this).rules("remove");
    });
}

$(document).ready(function() {
    $('form').validate({...});
    addRequired();
});

then hook some behavior on your triggering form element (which looks to be a radio button in your case) that when it's selected, call addRequired(). And when it's no longer selected then call removeRequired(). And obviously account for the different validation options on the back end.