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All those errors (except 12 which is ignition failure) are draft issues and could be related to a problem with the fan. If you're a newbie this is not something you should be messing with. Even a competent plumber needs extensive training before servicing one of these units. You risk making things worse or creating a hazardous situation. You can however set the dip switches which should be 2 ON & 3 OFF for your altitude. Only 2 & 3 relate to high altitude conditions.