Encoding problem

Hi List !

I am trying to remove accents from a string. I found a nice
solution for this on postgresqlfr, using the to_ascii()
function.

Now, the problem I have is :

mydb=# SELECT to_ascii(convert('abcdef', 'LATIN9'));
ERROR: encoding conversion from UTF8 to ASCII not supported

Why is the conversion to LATIN9 not working as expected ?
My database's encoding is UTF8.

Furthermore, in PgAdmin, running SELECT convert(somestring,
'LATIN9'); returns empty strings whenever somestring
contains special (accentued, in my case) characters.
SELECT Length(convert(somestring, 'LATIN9')); looks OK though !

I think my misunderstanding of encoding is driving me crazy...
Could anyone help me on this ?

Thanks !
--
Arnaud