[dpalomaki]

Does the car have a manual or automatic temperature selector for the HVAC controls?

The fan/coil unit contains two heat exchanger coils, one for cooling (evaporator coil) and one for heat (that has coolant circulating through it at all times). The outlet air temperature is adjusted by a mixing door that regulates the amount of air from each coil. Sounds like the door is stuck to allow mostly or only air from the heat coil.

In an automatic air temp car this could be caused by a bad door actuator/controller. On a manual air temp car it could be a failed or disconencted control cable somewhere at or between the door and the temp selector.