Hot air for passenger, cold air for driver (right hand side)

[Ray]

Hi legends,

I know there's a few threads already. But I'm trying to simplify it as doing a lot of reading and not seeing much helpful info. Dial is all the way on mad heat. No matter how I set the fans right hand side is blowing cool air andeft hand side blowing lava.

Is there a fix? If so, is it a dealer problem or home diy? Ta