My sisters 1993 BMW 5 series ac is cold, but we can barely feel any air coming out of the vents. Maybe 5% of normal.

Problem is the blower motor or resistor has gone bad

check the cabin air filter if equipped, Make sure that the air is not coming out of the floor vents or defrost. The door that diverts the air maybe stuck, pushing air out defrost/floor vents

time for brand new bmw. 20+ years is long enough to be messing with this old dinosaur.

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

check that the cabin filter is not blocked https://www.youtube.com/watch?v=UjSnUgC4cWI

Change your temperature setting to affect fan speed and on off mode. The Vapor is a problem on particularly humid days and effects Mercedes as well this too is affected by the temperature setting.

Try changing the thermostat

Hi check your ac blower ,fuse ,motor .

probably the vent in front of the blower motor lose, check that first.