A/c-Heater System - Automatic: Other — Ford Thunderbird X (1988-1997)

OFF

With OFF function control button depressed, display is off and outside-recirculated air door is in recirculating air position. Floor-defrost door is in floor (full vacuum) position. Blower is off and temperature blend door does not move.

MAX A/C (Recirculate)

With MAX A/C control button depressed, outside air door is closed to outside air (vacuum) and passenger compartment air is recirculated. Panel-defrost door is in panel position (vacuum) and air is distributed from instrument panel registers. Recirculating air is heated by selecting temperature on display.

NORM A/C (Outside Air)

When A/C function control button is depressed, outside-recirculated air door is opened to outside air. All other doors are positioned as in MAX A/C position and temperature is controlled in same manner.

VENT

With VENT control button depressed, outside air is directed through instrument panel registers. Control of discharge air temperatures is done in same manner as A/C position. In this position, refrigerated cooling is not available.

HEAT/FLR

With Heat/Floor (FLR) function control button depressed, airflow is directed to floor outlets. Some air is directed to windshield through defroster outlets. Outside-recirculated air door is in no-vacuum position and heat-defrost door is in full-vacuum position. Panel-defrost door is in no-vacuum position.

DEF/FLR

When Defrost/Floor (DEF/FLR) function control button is depressed, outside air is divided between defroster nozzle and floor duct outlets. Outside-recirculated and panel-defrost air doors are in no-vacuum position with heat-defrost door in partial vacuum position. Compressor clutch also engages to dehumidify air and reduce windshield fogging.

Defrost

When defrost symbol function button is depressed, A/C-defrost door and heat-defrost door are in full defrost no-vacuum positions. Incoming air is directed to defroster nozzle and side window demisters with some air bleed to floor. Temperature door is appropriately positioned. Compressor clutch also operates to dehumidify air and reduce windshield fogging.

Cool & Warm

Each time cool or warm button is depressed, temperature setting increases or decreases one degree.

In this position, system automatically regulates blower speed based on inputs from in-vehicle sensor, ambient sensor, sun load sensor and temperature set by driver.

Lo-Hi

These are manual blower override positions. System operates manually.

Scheme 2

Scheme 2: Lo-Hi

Blower Motor Speed Controller

The blower motor speed controller, located at bottom rear of blower motor housing, regulates blower speed when setting is in AUTO position to maintain desired temperature.

Clutch Cycling Pressure Switch

Clutch cycling pressure switch is mounted on top of suction accumulator-drier assembly. A Schrader valve depressor (at end of switch) presses in on Schrader valve stem, allowing suction pressure inside accumulator-drier canister. Switch contacts are open when suction pressure is approximately 24.5 psi (1.8 kg/cm 2 ) and close when suction pressure reaches approximately 47 psi (3.3 kg/cm 2 ) or greater. Switch controls current to compressor clutch and, when working properly, maintains evaporator surface temperature slightly above freezing.

Cold Engine Lock-Out Function

During cold weather, engine coolant temperature switch controls cold engine lock-out function when ATC system is set for AUTO operation. During lock-out, fan will not operate until engine coolant temperature is above 100°F (38°C). Switch is located in heater inlet hose.

Evaporator Core

Evaporator core is a multipass plate/fin-type core, mounted in a vertical position. Vaporized refrigerant enters core at lower corner and flows through first 3 plate/fin sections to opposite end of evaporator core.

Refrigerant flow then reverses and flows through next 3 plate/fin sections to other end of evaporator core, where flow again reverses to flow through remaining 4 plate/fin sections to suction tube. This S-type pattern accelerates refrigerant flow through evaporator core. There is no bleed line.

Fixed Orifice Tube

Fixed orifice tube assembly transforms high pressure liquid refrigerant to low pressure liquid refrigerant, while metering liquid refrigerant flow into evaporator core.

Fixed orifice tube, located in liquid line near condenser, has filter screens on its inlet and outlet ends. Adjustments or repairs cannot be made to the orifice tube. Orifice tube cannot be separated from liquid line. If defective, tube must be replaced.

Sensors

The ATC system uses 3 sensors: an ambient temperature sensor (located on a bracket on condenser), an in-vehicle temperature sensor (located behind instrument panel to left of glove box) and a sun-load sensor (located on left windshield defroster bezel). Sensors are thermistors that provide input for control assembly.

Thermal Limiter Resistor

Blower motor thermal limiter resistor is located on passenger's side of evaporator case, behind glove box. Three resistance elements are mounted on resistor board to provide 4 blower speeds. Series resistance is added or by-passed to increase or decrease blower speed. Thermal limiter is an overheating protection device. Overheating of resistor element normally takes place when system airflow is stopped due to blower motor lock-up. Whenever resistor circuit is opened, unit must be replaced.

"E1" CODE

Replace control head.

"E2" CODE

Blend door cannot reach desired position (within 20 seconds).

"E3" CODE

In-vehicle temperature sensor has open circuit.

"E4" CODE

Ambient temperature sensor has open circuit.

"E5" CODE

Sun-load sensor has short circuit.

"E6" CODE

Blend door travel is out of range.

"E7" CODE

Blend door cannot calibrate (cannot reach complete stops).

"E8" CODE

In-vehicle temperature sensor has short circuit.

"E9" CODE

Ambient temperature sensor has short circuit.

ALL SEGMENTS ON CODE

Testing is complete, no failures found.

If an intermittent failure has occurred during normal operation, but is not present during self-diagnosis, temperature control assembly displays one or more of the following codes (these codes are stored)

"P2" CODE

Blend door cannot reach desired position (within 20 seconds).

"P3" CODE

In-vehicle temperature sensor has open circuit.

"P4" CODE

Ambient temperature sensor has open circuit.

"P5" CODE

Sun-load sensor has short circuit.

"P6" CODE

Blend door travel is out of range.

"P7" CODE