The temp blend door rotates between allowing heat through the heater core, or cold air through the a/cevaporator, or a blending of the 2 by being anywhere between the two.
I would check the heater a/c control head first and hope it's just the control head.
here is a descripton of the system.
Section 12-03A: Air Conditioning, Heater System, Manual, Ranger and Explorer
1996 Ranger and Explorer Workshop Manual
DESCRIPTION AND OPERATION
A/C-Heater System, Manual
The manual air conditioning/heater system used in these vehicles is a split-case, blend air design. This design includes the following major components:
- An A/C evaporator housing (19850) which is attached to the engine compartment side of the dash panel (01610). This assembly includes: (1) the A/C evaporator core (19860), (2) the suction accumulator/drier (19C836), (3) the A/C cycling switch (19E561), (4) an internal, A/C evaporator core orifice (19D990) located inside the inlet line to the A/C evaporator core, (5) a blower motor (18527), (6) a blower motor wheel (18504), (7) a heater blower motor switch resistor (18591), and (8) the A/C evaporator case (19897).
- A heater air plenum chamber (18471) which attaches to the passenger compartment side of the dash panel. This assembly includes: (1) the outside/recirculating air inlet door, (2) the panel door, (3) the floor defrost door, (4) the temperature blend door, and (5) the heater core (18476).
- Other components which link and/or control the heating and air conditioning systems include: (1) the A/C control (19980), (2) the ducts and registers, (3) the windshield defroster hose nozzle (18490), (4) the control cables, (5) the vacuum lines, (6) the refrigerant tubes and hoses, (7) the A/C compressor (19703), and (8) the A/C condenser core (19712).
The A/C control (19980) assembly consists of three main parts:
- The function selector knob, a vacuum selector valve combined with an internal electrical switch.
- Heater blower motor switch (18578), an electrical switch that provides four speeds of A/C blower motor operation.
- A temperature control knob, which controls the position of the temperature blend door mounted on A/C evaporator housing (19850) assembly.
The temperature selector actuates a variable resistance switch. This switch varies the voltage to an electric actuator used to position the temperature blend door.
Positioning the temperature control in any position between COOL and WARM causes the temperature blend door to direct more or less outside air through or around the heater core (18476) for whatever proportion of heated or unheated outside air is desired.
The air blends together as it leaves the heater core and enters the heater air plenum chamber (18471) for distribution.
System Airflow Description
Air is drawn into the system by the blower motor (18527) through the outside-recirc. door opening. The air is blown through the A/C evaporator core (19860) and then the heater core (18476) (when the temperature control is moved toward the WARM position). When the temperature blend door is in the maximum COOL position, the air bypasses the heater core. When the temperature control is moved to the right, away from the maximum COOL position, air passes through the heater core where it is warmed, and then mixed with the cool air before it is discharged through the registers.
With the function selector in the OFF position, the outside-recirc. door is in the recirculated air position. It is closed to outside air and no air passes through the system. The blower motor is off.
NOTE: No temperature modulation is possible in the MAX A/C position.
In the MAX A/C position, the outside-recirc. air door is in the recirculated air position. All of the air discharges through the panel registers except for a small amount of floor bleed. The A/C compressor (19703) operates in this function control setting.
You have to almost remove the dash to get this part out.
Disconnect battery ground cable.
NOTE: Refer to Section 01-12 for instrument panel removal and installation procedure.
Loosen instrument panel (04320) and pull back from cowl.
Remove A/C electronic door actuator motor electrical connector from bracket on A/C evaporator housing.
Remove three A/C electronic door actuator motor retaining screws.
NOTE: The mounting bracket remains in place on the A/C evaporator housing.
Lift A/C electronic door actuator motor vertically approximately 12mm (1/2 inch) to disengage it from bracket and actuator shaft, then pull A/C electronic door actuator motor back toward passenger compartment.