The answer to 'furnace blowing cold air' is that there are several common causes, including a malfunctioning thermostat, a problem with the furnace's ignition system, a blocked air filter, or an issue with the blower motor. Symptoms may include the furnace not heating properly, the air coming out feeling cold, and the furnace cycling on and off frequently.
Some potential solutions homeowners can try include checking the thermostat settings, replacing the air filter, and clearing any blockages or debris around the furnace. However, if the issue persists or you're unsure of the cause, it's best to call a professional HVAC technician to diagnose and repair the problem.