Turned on my heat this morning and it's blowing hot air out of the passenger side like normal but the air coming out of the driver side vents is cool. Happens on both the upper dash vents and lower foot area vents. I also checked the defrost vents and they also blow cooler air (from all vents). My guess would be that its some directional valve behind the dashboard and not something like the heater core or thermostat since I am getting some hot air. Can anyone help?