Angular.js $http intercept “net::ERR_CONNECTION_REFUSED”

You can probably check the status of the ResponseError. When an API is offline that is 0 (until Angular 1.3.18) or -1 (since Angular 1.3.19):

angular.module("services.interceptor", arguments).config(function($httpProvider) {
     $httpProvider.interceptors.push(function($q) {
        return {
          responseError: function(rejection) {
                if(rejection.status <= 0) {
                    window.location = "noresponse.html";
                    return;
                }
                return $q.reject(rejection);
            }
        };
    });
});