Problem with inflator

I recently purchased an Axis BC. Last weekend I used it for the first time in Cozumel. When on the surface I had no problem dumping air when holding the inflator up and using the deflator. However as soon as I would go underwater, it would fail to purge any air. I ended up having to use the dump valves on the back of the BC if I needed to lose a little air.

As I am fairly new to diving and the Sherwood line - is there something I am doing wrong? I have not had problems with rented BC's by other manufacturers. Otherwise I am very satisfied with the BC.

Thanks,

MAtt

Take it to your dealer