Heater blowing cold air

Hello, it could be quite a few things; I'd be looking at your temperature blend door motors in the vehicle to see if maybe one or more is not turning to full heat. Also, check your rear ventilation system - does it blow heat when set? That one uses a separate temperature blend actuator. Professional hands on testing will really be able to tell a lot in s short period of time. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops