The answer to 'duct cleaning blowing cold air' is that this issue is often caused by a problem with the HVAC system's airflow. When duct cleaning is done improperly, it can disrupt the delicate balance of the HVAC system, leading to cold air being blown instead of the expected warm air.
Some common causes include blockages or restrictions in the ductwork, a problem with the blower fan, or an issue with the thermostat or other HVAC controls. In some cases, the duct cleaning itself may have dislodged debris that is now restricting airflow. If the problem persists after duct cleaning, it's best to call in a professional HVAC technician to diagnose and resolve the issue.