no heater (airflow) from passenger side airvents

[Azeem]

Hi,

I have noticed that if I put the AC on airflow from center air vents is fine. The issue is when I put the heater on there's no air flow from passenger side vents (including side vent from passenger side). Its a right hand drive car.

What could be the issue for no heated air from passenger side vents?

Thanks in advance.