Do you have a vacuum leak when going uphill the air blows threw the defroser when set for lower legs on heat?

Yes, it’s possible you have a vacuum leak if air is blowing through the defroster when the heat is set to lower legs while going uphill. This situation occurs because the vacuum system that controls the airflow direction may not be functioning properly, leading to a default position (usually the defroster) when there's insufficient vacuum pressure. It's advisable to check the vacuum hoses and connections for leaks or blockages to resolve the issue.