Ford Workshop Service and Repair Manuals

Three control units are available for Mondeo '97.

Vehicles without air conditioning (A/C) have the original control unit with three rotary switches. The temperature control flap is actuated mechanically by means of a Bowden cable. The air distribution is vacuum-controlled.

When the air distribution control switch is in the "OFF" position, the blower motor is also switched off regardless of the blower switch setting.

Control unit (vehicles without A/C)

On vehicles with manual A/C the functions of the rotary control knob from earlier model years have been retained.

Control unit (vehicles with manual A/C)

The control panel in vehicles with SATC (Semi Automatic Temperature Control) has two rotary control knobs, four buttons and a display.

The air distribution control switch performs the same functions as in the two other control units and additionally sends a signal to the microprocessor giving the "demist" flap position.

The buttons are used to select A/C and recirculated air mode and to select "warm" or "cold" air ranging from 18 - 29°C in one degree steps. Above and below these settings are the HI and LO settings which allow a minimum temperature of 15°C and a maximum temperature of 32°C to be set. The self-test can also be actuated by using a combination of these buttons.

The display shows the selected temperature, A/C and recirculated air mode and displays the fault codes in self-test mode. For additional information, refer to Section  412-00 Climate Control System - General Information. ”Diagnosis and testing

Control unit (vehicles with SATC)

Semi-Automatic Temperature Control

Semi Automatic Temperature Control is available as an optional extra in all Mondeo models.

A microprocessor inside the control unit evaluates the following input parameters and the signals emitted by the associated sensors:

• The selected settings on the control unit (temperature, air conditioning on/off, recirculated air mode, air distribution and blower speed).
• Passenger compartment temperature
• Ambient temperature
• Coolant temperature
• Sun load
• Vehicle speed

The following illustration shows the flow of signals to and from the control unit.

Signal flow

• In automatic mode the blower speed varies depending on the ambient temperature and a pre-set delay factor.
• Temperatures between 186,26C and 296,26C can be selected in 16,26C steps. Pressing the red button increases the temperature, whilst pressing the blue button reduces it. The system controls the temperature control flap and the blower speed accordingly.
• A self-test can be called up by pressing a combination of buttons ( For additional information, refer to Section  412-00 Climate Control System - General Information. ”Diagnosis and testing

Additional technical features of the control unit:

• LO setting (15°C) gives continuous cooling, HI setting (32°C) gives continuous heating.
• A/C button - this button switches the air-conditioning on and off respectively (depending on the current operating state).
• RECIRCULATED AIR button - this button is used to switch between recirculated air and fresh air modes respectively (depending on the current operating state).
• AIR DISTRIBUTION switch - to select the desired air distribution setting. In the DEMIST setting, the air conditioning automatically switches to fresh air mode. In the OFF setting, the fresh air flap (recirculated air mode) closes, and the blower motor and air conditioning controls will not function.

If the BLOWER regulator is switched out of the AUTO setting, the blower speed is no longer automatically regulated. It is then set manually by turning the regulator switch.

• In automatic mode, the blower is set to the optimum speed for the system's requirements.
• When it is set manually, the blower speed remains constant (depends on regulator switch position).

Operation

The semi-automatic temperature control (SATC) system automatically keeps the temperature constant at the level selected for optimum driving comfort and controls the supply of air to the following components:

• heat exchanger,
• heating ducts in footwell,
• windshield demister nozzles,
• side window demister nozzles.

The system incorporates the following control elements or functions:

• Switch for manual adjustment of the air distribution.
• Regulator for setting the blower speed manually or automatically.
• Sun load sensor which automatically measures the level of sunshine so that it can compensate for the resulting rise in temperature.
• Optimum operation is achieved in AUTO mode, where only the desired temperature is selected.
• If the passenger compartment temperature is lower than the selected temperature, the system automatically activates the heating (only when the engine is hot) in order to reach the selected temperature as quickly as possible.
• The air conditioning should be switched on if the ambient temperature is higher than 15°C or the passenger compartment temperature is higher than the selected temperature.
• Only change the selected temperature in gradual stages (1 - 2°C). This prevents large fluctuations in the passenger compartment temperature. Increasing the selected temperature by a large amount does not reduce the time it takes to reach the desired temperature.

Digital display

Depending on the selected setting, the digital display displays one of the following values:

• Selected A/C function, recirculated air mode and desired temperature.
• No display in the OFF setting.

Blue button (lower temperature)

The blue button is for reducing the temperature and works as follows:

• Pressing the button once reduces the temperature by 1°C.
• Pressing and holding the button down reduces the temperature in 1° steps as far as 18°C and in the next step to LO (15°C), i.e. maximum cooling capacity (continuous cooling).

Red button (increase temperature)

• Pressing the button once raises the temperature by 1°C.
• Pressing and holding the button down increases the temperature in 1° steps as far as 29°C and in the next step to HI (32°C), i.e. maximum heating capacity (continuous heating).

A/C button

• Pressing this button switches the air conditioning relay and the A/C symbol on or off (depending on the current operating state).
• The air conditioning relay will not come on if the ambient temperature is below -26,26C. If the A/C button is then actuated, the A/C symbol will flash to indicate this.
• The A/C symbol reappears when the temperature reaches 2°C, provided that the air conditioning relay has come on.
• In the DEMIST setting, the air conditioning relay is permanently on. The ambient temperature determines whether or not the A/C symbol is displayed.

Recirculated air button

• Pressing this button switches the recirculated air solenoid and the recirculated air symbol on or off (depending on the current operating mode).
• When the ambient temperature is above 2°C, the A/C symbol switches on and off together with the air-conditioning relay. If the A/C symbol and air-conditioning relay were already on, then they remain on. Both remain on after recirculated air mode is switched off.
• The A/C symbol does not appear when the ambient temperature is below -2°C. The air-conditioning relay does not switch on.
• The recirculated air function is not available during demisting. If the recirculated air button is then actuated, the recirculated air symbol will flash to indicate this.

Air distribution switch

Face-level only

The main airstream enters the passenger compartment at face level, and a small amount of air is directed to the side window demister nozzles.

Footwell and face-level

The main airstream is divided equally between the foot and face-level vents, and a small amount of air is directed to the side window demister nozzles.

OFF

In the OFF position, the air conditioning is completely switched off (the digital display is blank). The fresh air flap is closed (recirculated air mode).

Footwell

The main airstream is directed into the footwells, and a small amount of air is directed to the windshield and the side window demister nozzles.

Demist/footwell

The main airstream is equally divided between the windshield and the footwell vents, and a small amount of air is directed to the side window demister nozzles.

Demist

The main airstream flows to the windshield, and some air flows to the side window demister nozzles. The air conditioning relay is permanently on, the A/C symbol is displayed, depending on the ambient temperature, and recirculated air mode is not available.

Blower regulator

If the regulator is moved out of the AUTO setting by turning it more than 10° in the clockwise direction, automatic blower control is switched off and the blower speed can be set manually. The blower speed is increased by turning the regulator clockwise and decreased by turning it anti-clockwise. To return to automatic mode, turn the regulator back to AUTO.

Automatic mode

Automatic mode (semi-automatic temperature control) is switched on by:

• Turn the blower regulator to AUTO and press the A/C button. The ambient temperature must be above 2°C.
• The selected temperature and A/C symbol appear on the digital display.
• The selected temperature is kept constant by:
  -

  Regulating the volume of air (blower speed),
  -

  Regulating the temperature of the emerging air by means of the temperature control flap.
• Direct the main airstream into the footwell to increase the temperature (air distribution switch in footwell position). A small amount of the air will be directed to the windscreen and side window demister nozzles in the process.
• Direct the main airstream into the passenger compartment at face level to reduce the temperature (air distribution switch in face-level position). The nozzles can be adjusted. At maximum cooling power, the system automatically switches to recirculated air mode (providing the air-conditioning relay is on), before automatically switching back to fresh air mode once the desired interior temperature is obtained.
• In cold weather, the blower does not come on immediately after starting the engine, but only once the coolant reaches a temperature of 42°C, but no later than 3.5 minutes after starting the engine.

Pulse width modulator (PWM)

The pulse width modulator (PWM) module is used to regulate the blower motor speed and is located behind the blower housing.

The PWM supplies the blower motor with pulses of constant voltage and variable width. Narrow-width pulses result in slow blower motor speed, wide pulses result in high blower motor speeds. The PWM is triggered by the control voltage (5 V) switching on and off at a frequency of 2000 Hz. By varying the ratio of the ON/OFF time, the SATC control unit conveys to the PWM the required blower speed.

The PWM regulates the blower speed and has an overload cut-out switch which protects the blower motor from overheating and damage if a blockage occurs.

Temperature control flap actuator

The temperature control flap actuator is located on the inside of the evaporator housing and is connected to the temperature control flap.

• It adjusts the position of the temperature control flap in response to the signals sent by the control unit.
• The temperature control flap actuator contains a reversible electric motor and a potentiometer. The potentiometer brush is connected to the output shaft and moves together with it in order to feed the flap position back to the control unit.
• A voltage of 5 V is applied across the potentiometer. The brush divides this voltage according to the position of the flap. This smaller voltage is amplified and fed back to the control unit, thus informing the control unit of the current temperature control flap position. The control unit governs the temperature control flap actuator to the position required to obtain the desired temperature.

Sun load sensor

The sun load sensor is located on the right-hand side at the top of the instrument panel.

• It measures the intensity of the sunshine.
• The sun load sensor contains a photoelectric cell whose resistance decreases as the sun load increases.
• The photoelectric cell is part of a voltage divider which is fed with a voltage of 5 V. The voltage across the photoelectric cell is a measure of the sun's intensity and is fed to the control unit. The microprocessor in the control unit compensates for the sunshine in two ways: By adjusting the position of the air mixing flap and by increasing the blower speed.

Passenger compartment temperature sensor

The passenger compartment temperature sensor is incorporated in the instrument cluster.

• It measures the current temperature in the passenger compartment.
• It contains an electrically driven blower which sucks in air from the passenger compartment and directs it over an NTC element.
• The resistance of the NTC element decreases as the temperature increases. The blower is supplied with 12 V directly from the control unit. The NTC element is part of a voltage distributor which is supplied with a voltage of 5 V. The voltage drop at the NTC element is a measure of the passenger compartment temperature.
• This voltage is passed on to the control unit which adjusts the required passenger compartment temperature accordingly.

Engine coolant temperature sensor - air conditioning (ECT sensor)

The ECT sensor is located in the feed pipe to the heat exchanger.

• It measures the coolant temperature.
• The ECT sensor contains an NTC element. The resistance of the NTC element decreases as the temperature increases.
• The sensor is part of a voltage distributor which is supplied with a voltage of 5 V. The voltage at the NTC element is a measure of the coolant temperature. This voltage is passed on to the control unit, which increases the blower speed if the coolant temperature is low.

Ambient temperature sensor

The ambient temperature sensor is installed in the front bumper.

• It measures the external temperature.
• The ambient temperature sensor contains an NTC element. The resistance of the NTC element decreases as the temperature increases.
• The sensor is part of a voltage distributor which is supplied with a voltage of 5 V. The voltage at the NTC element is a measure of the ambient temperature. This voltage is passed on to the control unit, which uses it to control the passenger compartment temperature.

Recirculated air solenoid

The recirculated air/air intake solenoid is fitted on the evaporator housing.

• It blocks or releases the vacuum to the recirculated air flap vacuum actuator.
• It consists of a magnetic switch which operates a valve.
• The recirculated/air intake solenoid is supplied with a voltage of 12 V. It is switched on by the control unit when the circuit is connected to ground (GND). To switch it off, the circuit is disconnected from ground.

Air distribution switch

The air distribution switch is part of the control unit.

• It directs the main airstream to the selected outlet(s).
• The air distribution switch combines electrically and pneumatically controlled functions. The air distribution is controlled pneumatically.
• In the OFF setting, the control unit and blower are switched off. In the DEMIST setting, a signal is sent to the control unit to disable RECIRCULATED AIR mode and switch on the air conditioning. Both functions are controlled electrically and pneumatically.

Vacuum diagram