Vents blow cold out passenger side only

I am assuming your vehicle is equipped with a “dual zone” climate control system, which allows you to have a different temperature, if desired, in the passenger side zone versus the driver’s side zone of the vehicle. When one side will not adjust to the proper temperature, there is either a problem with the control mechanism, the motor that turns the doors behind the dash inside the ventilation system plenum which meters the temperature from hot to cold, or a problem with the actual doors or plenum. Testing will need to be performed to find out what has failed and how it can be repaired. https://repairpal.com/repair-shops/buick-repair-and-service-in-anaheim-california