Air works fine on 97 Lincoln continental but heat does not work

Probably needs a heater core replacement. Check and make sure your coolant level is good. There are two hoses that enter the passenger side firewall. With the engine at operating temperature feel both hoses. If both are about the same temo the core is fine. If one is hot and the other is cool then heater core is clogged and will need to be flushed or replaced. Replacement is very expensive on most vehicles. The part is usually cheap...around $50...the labor is high. The entire dash board of the car has to be removed to replace the heater core. Most vehicles take around 10 hours of labor time to do.