When operating air conditioner, hot air comes out on the driver side, the passenger side is normal. What is my problem?

The "dual coolant control valve" needs to be replaced. This is what the T-bird has rather than a "blend door" or a "blower door" like other dual temp climate control systems. It's buried under a bunch of other stuff in the passenger side front of the engine and has about 3 heater hoses connected to it. A serious DIYer can do it (I did) but it was a royal PIA.