hot air from the driver side vents

[bankswood]

Hi all, been awhile since I was on the forum. My son took my Tahoe so I haven't had reason to visit the site. My neighbor has a 2003 Tahoe and it has started blowing hot air out of the driver side vents when the air con is on. Passenger side blows cold. It occasionally blows cold but most of the time it blows hot. Can someone direct me to a fault/failure/cure.
TIA

 

[pyrophil]

it's a actuator gone bad there is several write ups on this