I recently purchased a 95 Mustang for $750 but I'm having a little problem. They AC/Heat will run but it's only blowing cold air and only through the defrost. It won't blow through the vents or any warm air.

 

Verify heater hose's are connected to heater core by firewall. Not that a po disconnected them because of a leaking heater core.

Next, verify you hear the vacuum assisted doors open or close under the dash by turning on the heater, to defrost back to heater. Maybe a vacuum line came off.