2000 Mazda MPV, rear heater is not working, AC is. What could cause?

Hello, the rear heater and air conditioner has a mechanism to blend hot and cold temperatures just like the front of the vehicle ventilation system. Although there could be a problem with hot coolant reaching the heater core in the rear of the vehicle, it is more likely that the temperature blending mechanism is malfunctioning, be it from the controls or the motor that moves the blending door back and forth depending on desired temperature. Have this checked. www.repairpal.com/repair-shops

Research- Heater Control Valve.