It appears you live in a very warm climate. None the less is it possible that the A/C gets the cabin down to the temperature you've set in the HVAC control and then automatically reduces the fan speed and cooling effect? This would be acting as BMW designed it; cool quickly then reduce cooling to just enough to maintain the set temperature. Your description of "for a while" sounds as though this might be the case.My AC is normally working fine but sometimes after driving the car with the AC on, for a while, the air blowing will be less & the cooling will also be much less. Any idea about the cause of this problem?
A second thoughtMy AC is normally working fine but sometimes after driving the car with the AC on, for a while, the air blowing will be less & the cooling will also be much less. Any idea about the cause of this problem?
It doesn't sound like the classic FSU symptoms ... but, just in case, the OP will benefit from a quick /FSU(F3) in the bestlinks:I'd bet my left one the FSU is dying.
I think you are right, the fan is not slow but the air blowing is less.A second thought
I made an assumption that when you described "the air blowing will be less" that the fan slowed down. However, it is possible that air flow could be reduced if the evaporator iced up and thus blocked/reduced air flow out the vents, even though the fan is still on high speed.
Does the fan slow?
The A/C system is designed so that icing should not ever occur, i.e. that evaporator temperature is never less than ~3-4C. Unless that is, a part or parts are defective.
If so, you will need specialized equipment &/or an A/C expert to make repairs.