BMW X3 AC only cool air on driver side

Being a 2006 BMW, I don't know if you really want to tear into the dash compartment. Your AC is working fine, the problem with the unit is your heater control valve under the dash is faulty. you cant fix it but replace it the cost with single solenoid 85 bucks and dual solenoid is 172 buck; your would have two because your car equip with his and hers climate control; without proper tools to work on the car taking the dash apart is a task especially you have to know every bolt location. The unit is not adjusting the valve like it suppose to. The valve work like and normal valve, same as your faucet at home on or off. the valve is not shutting off fully due to solenoid faulty or the valve it self is stuck,jam or not sealing and that is the reason why you still getting warm air. I can assure you if you turn the ac button off and let the fan run only you will get nothing but hot air, the air seem warm because is mixing with with the cold air from your evaporator. hope that help some, good luck

There is a divert valve to control a flap directing air thru either heater coil or Evaporator depending on when you select heater or AC . Either the cable holding the Flap or the valve is not working. Need to check this out- a lot of work through behind the center vent. Good luck

Check your owners manual under DUAL ZONE CLIMATE CONTROL your passenger may have change settings