I have the same de-humidefier and I am not all that sure it is working. It doesn't seem to be pulling the water out of the air as much as it did. However, I am monitoring the humidity from a seperate instrument and it seems to be OK. My de-humidefier is also making a rattling noise, I think on defrost. I was looking to see if you can take it apart and clean it. I am using it second hand and I have had it 3 years and it has never been cleaned in that time.
Have you got anywhere with your one?
Kev, December 2008