Your model should just have coolant flowing directly into the core at all times. A simple check of the flow is to feel both heater hoses going into the firewall from a cold start. The hoses should warm up at about the same rate and get uncomfortably hot. This is a good indication that heat is getting into the passenger compartment.
If it appears that the core is getting hot, the next suspect is the blend door. This door diverts some or all of the air flow through the heater core and commonly fails on the Mountaineer/Explorer/Ranger/Mazda pickup...all of which use the same plenum box. The door is on a vertical axis and has a pervasive problem with the the plastic connection to the motor breaking. The door can swing back and forth randomly or wedge in a strange position, killing heat and AC efficiency. This is an expensive dealer repair, but there is an aftermarket repair kit from HeaterTreater that will address and solve the problem. Complete diagnostic information and diagrams are available.
you need to change your thermostat
It may have a bad heater core.
You need to change your thermostat in the car.
air is blowing bat problem is no air com to front only in class
It is because your heater is having to heat up so its blowing cold air out while its heating up.This means your heater is not very efficient and it needs to be checked.
Most likely a replacement heater core
this is not an answer just an update. coolant is filled
check your coolant level. if its full, might be a plugged heater core.
is the blower motor running? or is it just not blowing hot air?
Is it not hot? Not blowing? Leaking coolant? Need more info to help you.
Check the temperature control cable
heater core plugged or air locked check to see if hoses going to heater core are hot