Help with prototype Ajax.Request function

Part 1 of the script not posted here simply contains the vars.
Part 2 of the script not posted here simply loops through the html form and sets up the event listeners eg:
 
$(elementList[n].id).observe('blur', respondToBlur); //triggers the validation request.
 
respondToBlur calls:
goValidate(element); //do the ajax request
 
Part 3 of the script is my ajax request:
 
	function goValidate(element) { 
	
		// 1. prepare the ajax Request
		var actionURL = action; // the php validation script
		//var actionURL = action + '?id=' + element.id + '&value=' + $F(element);
	
		// 2. now do the ajax Request
		new Ajax.Request(
			actionURL, //url
			{
			
			//method:method,
			parameters:Form.serialize(formID), // this takes all the POST fields and sends them to the controller.php
			asynchronous:true,
			requestHeaders: ['Cache-Control', 'no-cache', 'Pragma', 'no-cache'],
 
			onComplete: function(request) {
				// check the incoming literal string format eg pass|Good message or fail|Sorry bad message and update accordingly
				var fullMessage = request.responseText;
				var myArray = fullMessage.split('|'); //split items at comma to array
				var successCode = myArray[0]; // fail or pass
				var messageText = myArray[1]; // eg good message
				if (successCode == 'pass') {
					// 1. successful validation, now UPDATE THE MESSAGE FIELD
					if (messageText) { 
						$(updateElem).innerHTML = messageText; // add message to message div
					}
 
				} else if (successCode == 'fail') { // PHP validation failed
					// 1. validation failed so update the message field
 
					if (messageText) {
						$(updateElem).innerHTML = messageText; // add message to message div
					}
 
				} else {
					//system failure!
					alert("Ooops, something went wrong with the PHP response as no error code was found - probably a config or server error so better log something! " + fullMessage);
				}
			
			}	
		});	
	
		//only do this validating part when the first stage of the ajax request has been sent.
	}//ends function goValidate