This was my exact problem, hot rear vents, cold front face vent.I am referring to “process of elimination”.
Rear vent is blowing hot hot air, while the face is blowing cold air, surely this symptom not the coolant level. So we can eliminate that as a root cause?
The above issue is what many are observing. Throwing out the “top off coolant” solution doesn’t add value for this kind of issue, no?
Cold foot vent warm/hot face vent.
Hot feet, cold screen.
So to your question, the system can blow hot and cold at the same time. They had to bleed mine 3-4 times to get right. Persistence is required by the dealer to get working properly