AP

I'm not sure what is happening... but when i turn the AP master switch on the plane radicly increases altitude like the world is blowing up!!! 8-)
when i set the altitude in the AP it dosnt do as i say.... nor does it take the correct heading or speed... :-? now maybe im just crazy or not really sure how to use AP (which i dont, never do unless i'm doing somthing else at the same time) at all!!! :-/ is anyone else having this problem or am i just paranoid??!!?? 

