Air Condition & Heater not blowing right temp

Hi, this is my first post so go easy on me.

I just recently got a 1998 740iL, and during the day, when i'd like to run my AC, it only seems to blow hot air, then, during the night, when i'd like to run the heater, it only blows cold air.. It doesn't matter what temperature I have it set to on either the driver or passenger side.

I'm assuming it's just not conditioning the air whatsoever.. seeing that in the day (when it's hot outside) it blows hot air, and at night (when it's cold) it blows cold air.

I was thinking I should just replace the AC fuses, but I wanna know if you guys have any suggestions. Thanks guys.

Jay