Part 1

Climate Control System

WARNING: Take the following precautions when repairing an air conditioning system containing R-134a:
- Always wear safety goggles.
- Avoid contact with liquid refrigerant R-134a. R-134a vaporizes at approximately -25°C (-13°F) under atmospheric pressure and will freeze skin tissue.
- Never allow refrigerant R-134a gas to escape in quantity in an occupied space. It will displace the oxygen needed to support life.
- Never use a torch in an atmosphere containing R-134a gas. R-134a is non-toxic at all normal conditions, but it decomposes when exposed to high temperatures such as a torch flame. During decomposition it releases irritating and toxic gasses (as described in the MSDS sheet from the manufacturer). Decomposition products are hydrofluoric acid, carbon dioxide and water.

Failure to follow these instructions may result in serious personal injury.

NOTICE: To avoid damaging the vehicle or air conditioning (A/C) components, the following precautions must be observed.
- The A/C refrigerant of all vehicles must be identified and analyzed prior to refrigerant charging. Failure to do so can contaminate the shop bulk refrigerant and other vehicles.
- Do not add R-12 refrigerant to an A/C system that requires the use of R-134a refrigerant. These 2 types of refrigerant must never be mixed. Doing so can damage the A/C system.
- Charge the A/C system with the engine running only at the low-pressure side to prevent refrigerant slugging from damaging the A/C compressor.
- Use only R-134a refrigerant. Due to environmental concerns, when the A/C system is drained, the refrigerant must be collected using refrigerant recovery/recycling equipment. Federal, State/Provincial and/or local laws REQUIRE that R-134a be recovered into appropriate recovery equipment and the process be conducted by qualified technicians who have been certified by an approved organization, such as ASE or Mobile Air Conditioning Society (MACS). Use of a recovery machine dedicated to R-134a is necessary to reduce the possibility of oil and refrigerant incompatibility concerns. Refer to the instructions provided by the equipment manufacturer when removing refrigerant from or charging the A/C system.
- Refrigerant R-134a must not be mixed with air for leak testing or used with air for any other purpose above atmospheric pressure. R-134a is combustible when mixed with high concentrations of air and higher pressures.
- A number of manufacturers are producing refrigerant products that are described as direct substitutes for Refrigerant R-134a. The use of any unauthorized substitute refrigerant can severely damage the A/C components. If repair is required, use only new or recycled Refrigerant R-134a.


NOTICE: To avoid contamination of the air conditioning (A/C) system:
- Never open or loosen a connection before recovering the refrigerant.
- When loosening a connection, if any residual pressure is evident, allow it to leak out before opening the fitting.
- Evacuate a system that has been opened to install a new component or one that has discharged through leakage before charging.
- Seal open fittings with a cap or plug immediately after disconnecting a component from the system.
- Clean the outside of the fittings thoroughly before disconnecting a component from the system.
- Do not remove the sealing caps from a new component until ready to install.
- Refrigerant oil will absorb moisture from the atmosphere if left uncapped. Do not open an oil container until ready to use and install the cap immediately after using. Store the oil in a clean, moisture-free container.
- Install a new O-ring seal before connecting an open fitting. Coat the fitting and O-ring seal with mineral oil before connecting.
- When installing a refrigerant line, avoid sharp bends. Position the line away from the exhaust or any sharp edges that can chafe the line.
- Tighten threaded fittings only to specifications. The steel and aluminum fittings used in the refrigerant system will not tolerate overtightening.
- When disconnecting a fitting, use a wrench on both halves of the fitting to prevent twisting of the refrigerant lines or tubes.
- Do not open a refrigerant system or uncap a new component unless it is as close as possible to room temperature. This will prevent condensation from forming inside a component that is cooler than the surrounding air.


The manual climate control system heats or cools the vehicle depending on the function selector switch position and the temperature selected.

- The function selector switch position determines heating or cooling, air distribution and enables blower motor operation.
- The temperature control setting determines the air temperature.
- The blower motor switch varies the blower motor speed.

The Dual Automatic Temperature Control (DATC) system maintains the selected vehicle interior temperature by heating and/or cooling the air.

- During A/C operation the system also reduces the relative humidity of the air.
- The driver may override the automatic mode of operation.
- The driver side and passenger side temperature settings can be individually controlled.

The system components are the following:

- A/C compressor
- A/C compressor clutch assembly
- A/C condenser core
- A/C evaporator core
- Suction accumulator
- Connecting refrigerant lines
- A/C evaporator core orifice
- A/C cycling switch
- A/C pressure transducer
- Heater core and evaporator core housing
- HVAC module - DATC
- Manual climate control assembly
- Blower switch (manual system)
- Temperature blend door actuator(s)
- Blower motor resistor or speed control module
- Blower motor
- Ambient temperature sensor
- In-vehicle temperature sensor
- Solar radiation sensor
- Auxiliary connecting refrigerant lines
- Auxiliary heater core and evaporator core housing
- Auxiliary A/C evaporator core
- Auxiliary climate control assembly
- Auxiliary blower motor
- Auxiliary blower motor resistor


Climate Control System Operation


Manual Climate Control System

The manual climate control system operation is determined by the settings on the climate control assembly. The climate control assembly includes a serviceable function selector switch and blower motor switch. The temperature control switch, A/C request switch and rear window defrost switch are integral to the climate control assembly and are serviced as an assembly.

The blower motor switch:

- sets the front blower motor speed.
- directs the blower motor path to ground through the blower motor resistor to allow blower motor operation in LO, MED-LO and MED-HI.
- actuates the high speed blower motor relay, giving the blower motor a direct path to ground which allows the blower motor to operate in HI.

The temperature control switch:

- is a potentiometer that outputs a variable voltage to the temperature blend door actuator to set the position of the temperature blend door.
- initiates closing of the heater control valve. When set to full COOL, a lever on the temperature blend door pivot shaft depresses the pintle of the heater control valve vacuum switch. The heater control valve vacuum switch then applies vacuum to the heater control valve, closing off engine coolant flow to the heater core.
- is serviced only with the climate control assembly.

The function selector switch setting:

- determines where the system airflow is directed.
- enables blower motor operation.
- enables auxiliary blower motor operation, if equipped, by supplying voltage to the auxiliary blower motor relay.
- commands A/C compressor operation in MAX A/C, FLOOR/DEFROST and DEFROST.

The A/C request switch:

- can command the A/C compressor on when the function selector switch is in PANEL, FLOOR/PANEL and FLOOR when the A/C request switch is pressed.
- is inoperative in MAX A/C, OFF, FLOOR/DEFROST and DEFROST.
- indicator illuminates when the function selector switch is in MAX A/C and cannot be toggled.
- indicator does not illuminate in OFF and cannot be toggled.
- indicator does not illuminate in FLOOR/DEFROST and DEFROST and cannot be toggled. The A/C compressor will not operate if the outside air temperature is below -1°C (30°F). The A/C compressor will resume operation when the outside air temperature rises above 2°C (35°F).
- is serviced only with the climate control assembly.


Dual Automatic Temperature Control (DATC) System

The DATC system maintains the selected vehicle interior temperature by heating and/or cooling the air.

- During A/C operation the system also reduces the relative humidity of the air.
- The driver may override the automatic mode of operation.
- The temperature control setting determines the desired air temperature.
- The blower motor control override buttons vary the blower motor speed.
- The driver side and passenger side temperature settings can be individually controlled.

The DATC system operation is determined by the settings on the HVAC module - DATC. The DATC system automatically maintains a selected temperature for vehicle interior comfort, including capabilities to maintain separate temperature settings for the driver and front passenger. The electronic temperature control capabilities are achieved by splitting the air distribution system internally and utilizing 2 individually operated temperature blend doors. The DATC system is composed of the HVAC module - DATC, solenoid and manifold assembly, blower motor speed control, 4 vacuum control motors, 2 temperature blend door actuators, in-car temperature sensor, ambient air temperature sensor and solar radiation sensor to control the various functions.

When the HVAC module - DATC is set to AUTO:

- the air distribution direction, heater control valve operation and blower motor speed are automatically controlled based on the temperature(s) selected.

The HVAC module - DATC manual override settings:

- allow the air distribution direction to be manually selected.
- allow the blower motor speed to be manually selected.
- allow RECIRCULATION mode to be manually selected except in FLOOR/DEFROST and DEFROST. The A/C request can be cancelled by pressing the A/C request switch, turning the indicator off.
- allow A/C compressor operation to be manually selected except in FLOOR/DEFROST and DEFROST.

The HVAC module - DATC also includes:

- an EXT button to monitor ambient (outside) air temperature. By pressing the EXT button the ambient temperature will be displayed on the HVAC module - DATC display until the EXT button is pressed again.
- a F°/C° temperature conversion button to toggle the temperature being displayed from Fahrenheit and Celsius.
- a rear window defrost button (Explorer only). Refer to Windows.

Dual temperature control can be enabled in AUTO or in all manual override settings. When the HVAC module - DATC is set to DUAL:

- the DATC system enables varying temperatures to be selected by the driver and the front passenger. Dual temperature control is indicated by the presence of 2 temperature settings on the HVAC module - DATC display. To return to single temperature control press the DUAL button, turning the DUAL button indicator off and the front passenger temperature display off.
- the air distribution direction and the blower motor speed cannot be varied between the driver and front passenger. Only the temperature settings can be varied.
- the system will favor the driver temperature setting if the driver and front passenger temperature set points vary greatly.

External Temperature Display

The external temperature is displayed when the EXT button is pressed. While the actual external temperature can vary continuously, the value that is displayed will update at a specific rate depending on whether or not the engine is "hot" and whether or not the vehicle is moving.

When the external temperature is rising, the display will update slowly.

Updates (when the actual external temperature is higher than currently displayed value) will be limited to 0.6°C (1°F) every 20 seconds while the vehicle is moving at greater than 40 km/h (25 mph) for more than 90 seconds OR 0.6°C (1°F) every 20 minutes if the vehicle is not moving at this speed. This is to prevent the heat from the engine compartment from affecting the accuracy of the display.

When the external temperature is dropping, the display will update quickly.

Updates (when the actual external temperature is lower than currently displayed value) will only be limited to 0.6°C (1°F) every 2 seconds (regardless of vehicle speed). Consequently the display will essentially follow the drop experienced by the external temperature thermistor.


Auxiliary Climate Control System

NOTE: Auxiliary climate control system not available on Sport Trac model.

An auxiliary climate control system is available as optional equipment. The auxiliary climate control system operation is determined by the settings on the front auxiliary climate control assembly. The auxiliary climate control assemblies include a blower motor switch, temperature control switch and air distribution mode switch, none of which can be individually serviced.

On vehicles with manual climate control the auxiliary blower motor operation is enabled when the function selector switch is in any position except OFF. The auxiliary system air can be cooled below ambient temperature only when A/C compressor operation has been requested by the settings of the climate control assembly of the base (front) system. The auxiliary system air can be heated at any time, the heater control valve does not affect the auxiliary climate control system operation.

On vehicles with DATC the auxiliary blower motor is operational regardless of the DATC system setting. The auxiliary system air can be cooled below ambient temperature only when A/C compressor operation has been requested by the settings of the HVAC module - DATC. The auxiliary system air can be heated at any time, the heater control valve operation does not affect the auxiliary climate control system.

The front auxiliary climate control assembly:

- blower motor switch controls the auxiliary blower motor speed. The blower motor speed can be set to OFF, MED-LO, MED-HI or HI.
- air distribution mode switch toggles airflow between the overhead vents and the floor vent by outputting signals to the auxiliary airflow mode door actuator which positions the auxiliary airflow mode door in all blower motor switch positions. Back-lit icons on the front climate control display indicate the source of the auxiliary system airflow.
- temperature control switch is a potentiometer that outputs a variable voltage to the auxiliary temperature blend door actuator to set the position of the auxiliary temperature blend door in all blower motor switch positions. The temperature of the auxiliary system air may be affected by the manual climate control assembly or HVAC module - DATC settings (as equipped). When A/C compressor operation has not been initiated (A/C compressor commanded on) by the manual climate control assembly or the HVAC module - DATC (as equipped), the auxiliary climate control system cannot cool the air below that of the ambient temperature.