Go through the access squence below and select c400 series the c-403L is the last on pdf page.
Download all by selecting save on each download. then open each saved pdf see if you can see the part if not then go back to around page 3 and click on ASK THETFORD. send them email explaining what happened and description of the part.
I took a look and the only white part I can see is the handle with a tube like part on the left side.
I doubt if it has come off the bowl and the access I assume you are talking access through the bottom of the bowl, as you say it's no possible the holding tank when removed has the blade in it and what's left is the bowl with a hole nothing else as far as I know.
INCASE YOU HAVEN'T DOWNLOADED BEFORE.
Once on you're on the C-403L pdf list start from the top click on the first one select save to save to your hard drive. follow on with each pdf file same as above. If you computer blocks popups then press Ctrl key and click at same time the file will come up as a pop up or as a closed popup above on the status/tool line click again to open
SEE TIP BELOW.
UK www.thetford-europe.com
Australia www.thetford.com.au (Even get request from Australian campers)
Australia site has stockist list.
HOME PAGE SELECT ENGLISH {if in Australia forget this selection)
NEXT PAGE SELECT CUSTOMER SERVICE (top line)
NEXT PAGE SELECT USER INFORMATION (left of pic) also 'Ask thetford' is on this page.
NEXT PAGE SELECT REPAIR INSTRUCTIONS (left of pic)
NEXT PAGE SELECT BUILT IN TOILETS [top right of pic]
NEXT PAGE SELECT This is where you select your toilet range. Search alll if unsure of type/range
NEXT PAGE PDF Files You should be in the pdf folder list on your Thetford toilet. Start downloading.
To direct link to the Thetford download site type in the following
www.thetford.eu/web/show/id=51498/langid=42
Don't bother for Thetford fridges they tell you for safety reason to take it to a service centre
Bob, January 2010
