Why does only cold air blow out in the rear of my 2001 mazda mpv?

If only cold air is blowing out of the rear vents in your 2001 Mazda MPV, it could be due to a malfunctioning blend door actuator, which controls the mix of hot and cold air. Another possibility is a low refrigerant level in the AC system, affecting its ability to produce warm air. Additionally, a blocked or malfunctioning heater core could prevent warm air from reaching the rear. It's advisable to have a professional diagnose the issue for a proper fix.