HVAC System - Heating & Ventilation: Other Ford Escape I

Temperature Control Knob

The temperature control knob mechanically operates a cable through a cam mechanism to adjust temperature blend door. Temperature blend door is in plenum assembly. When temperature knob is in cool position (turned fully counterclockwise), temperature blend door stops airflow to heater core. When knob is in warm position (turned fully clockwise), air is directed through heater core. When knob is in intermediate positions, heated air is blended with cooler incoming air to achieve desired temperature.

Function Selector Knob

Function selector knob can be placed in OFF, panel, panel/floor, floor, floor/defrost or defrost position. Function selector knob operates a vacuum switch connected to appropriate actuator motors, which operate floor/defrost and panel doors.

Outside/recirculation door is controlled by a vacuum valve and vacuum motor. When function selector knob is in OFF position, vacuum is applied to outside/recirculation door vacuum motor to shut off outside airflow. When function selector knob is in any other position, vacuum is not applied to outside/recirculation door vacuum motor and outside air is allowed to enter vehicle.

When function selector knob is in panel position, air inlet blend door, with no vacuum being applied, blocks recirculated air and allows in outside air. (Scheme 52) Air flows through system to driver, passenger and center registers. Vent/register blend door is at partial vacuum to direct airflow to driver, passenger and center registers. Defrost blend is at full vacuum and defrost airflow door is at no vacuum, closing off airflow to windshield defroster nozzles and footwell ducts. Temperature setting can be changed manually to heat air but air cannot be cooled below outside temperature. Blower motor is on.

When function selector knob is in off position, air inlet blend door is at full vacuum, closing off outside air and allowing only recirculated air. (Scheme 53) Vent/register blend door is at no vacuum and defrost, footwell and blend airflow doors are at no vacuum, closing off passages to driver, passenger and center registers. Blower motor is off.

When function selector knob is in panel/floor position, air inlet blend door is set at no vacuum, blocking recirculation passage and allowing outside air. (Scheme 54) Footwell blend door is in full vacuum position, and panel airflow door is in full vacuum position allowing airflow to blend between panel vents and footwell ducts. Defrost airflow door is at full vacuum, closing off airflow to windshield defroster hose nozzle and directing airflow to heater outlet footwell duct. Blower motor is on.

When function selector knob is in floor position, air inlet blend door is in no vacuum position, blocking recirculation air and allowing in outside air. (Scheme 55) Footwell airflow door is at full vacuum position, opening door and allowing airflow through footwell ducts. Defrost airflow door and vent/register blend door are in no vacuum position, closing off airflow to windshield defroster hose nozzles and driver, passenger and center registers. Temperature control can be positioned to mix air flowing through and around heater core to achieve selected temperature level. Blower motor is on.

When function selector knob is in floor/defrost position, air inlet blend door is in no vacuum position blocking recirculation air and allowing outside air. (Scheme 56) Footwell blend door is at full vacuum allowing air to flow through footwell ducts. Defrost blend door is in no vacuum position, allowing airflow to both windshield defroster hose nozzle and side window demister hose nozzle ducts. Vent/register blend door is in no vacuum position. Blower motor is on.

When function selector knob is in defrost position, air inlet blend door is in no vacuum position, allowing outside air. (Scheme 57) Defrost blend door is at no vacuum, directing airflow to windshield through defroster ducts and side windows through demister ducts. Panel airflow door and footwell airflow door are in no vacuum position so that most of incoming air is directed to windshield defroster hose nozzle. There is also airflow to side window demister and hose. Temperature control knob setting will determine amount of air that is directed through heater core and amount that bypasses heater core. Blower motor is on.

Scheme 52

Scheme 53

Scheme 54

Scheme 55

Scheme 56

Scheme 57

Blower Switch

Blower motor is controlled by a 5-position blower switch. 5 positions are off, low, medium-low, medium-high and high. Blower switch is turned off by rotating switch fully counterclockwise. 4 operating speeds are obtained with a blower motor resistor, connected in series with blower motor switch, operating on negative side of blower motor.

BLOWER MOTOR

Blower motor operating speeds (low, medium-low, medium-high and high) are controlled by a blower motor switch and resistor which determines blower speed by adding or by-passing resistors in blower motor switch resistor.

BLOWER MOTOR RELAY

Blower motor relay supplies voltage to blower motor and is activated when key is ON and function selector switch is in any position besides OFF.

Possible Causes

1. No vacuum to function selector switch.
2. Function selector switch leaks vacuum.
3. Vacuum line kinked/pinched.
4. Leaking vacuum control motor.
5. Leaking vacuum check valve.
6. Leaking vacuum reservoir tank.
7. Vacuum actuator arm not connected to door lever.

1. Low engine coolant level.
2. Engine overheating.
3. Plugged or partially plugged heater core.
4. Inoperative blend door.
5. Temperature control cable.

1. Temperature blend door actuator.
2. Temperature blend door binding/stuck.
3. Temperature blend door control cable damaged/disconnected.

1. Open fuse No. 23 (40 amp).
2. Circuit open/short.
3. Blower motor switch.
4. Blower motor resistor.
5. Blower motor relay.
6. Blower motor.

1. Circuit short/open.
2. Blower motor resistor.
3. Blower motor switch.

1. Blower motor resistor.
2. Blower motor switch.

1. Circuit short/open.
2. Blower motor resistor.
3. Blower motor switch.

HEATER CORE

Note. Inspect for evidence of coolant leakage at heater water hose to heater core attachments. A coolant leak in heater water hose could follow heater core tube to heater core and appear as a leak in heater core. Check integrity of heater water hose clamps.

FUNCTION SELECTOR SWITCH

Note. For circuit reference, see WIRING DIAGRAMS .

To check function selector switch operation (Scheme 58)

Scheme 58

Note. If a heater core leak is suspected, heater core must be leak tested before it is removed from vehicle. See HEATER CORE under COMPONENT TESTS.