Hi,

This is a refrigerated air dryer, working about the same as an air conditioning. Air is cooled down, condensate water is removed, and then the air is warmed up again.

It could be that the inside is dirty and full with mold and other nasty stuff.

You can start by opening and cleaning the condensate trap that should be inside the dryer. This will give you an idea how dirty the insides are.

Hope this helps!

Cas