1998 735i Heater issue, help would be great

[gf15]

Hi folks,
set heater controls on both sides + rear to cold with AC on, very cold air from all vents except the vent under the front passenger seat which blows schorching hot air onto rear passenger! rear passenger on driver's side works as it should

Any ideas would be appreciated!

[Marshy]

Set the blend control in the middle of the centre dashboard vents to hot... do you get warm air from all the passenger dash vents? If so, the heater control valve for the passenger side might be stuck... it's the widget under the bonnet that stops/starts (hot) coolant from circulating through the heater matrix.