Can a Palate Expander Cause an Open Bite?

Can a palate expander induce an open bite? My orthodontist is for some reason refusing to treat me with a palate expander and is using the idea that a palate expander may cause me to have an open bite? I find this a little far-fetched. This is particularly because my bite as it stands is not all that bad. I have a somewhat class III pattern, however my upper jaw does sit just slightly over my lower jaw. My problem is my molars do not meet and I need my upper jaw expanded. Should I get a second opinion?