Heating & Air Conditioning - Service Information: Overview Dodge Dart PF

DESCRIPTION

The HVAC housing is mounted longitudinally in the vehicle, which means it doesn't follow the line of the bulkhead, but protrudes into the passenger compartment. The assembly is available in a single or dual zone configuration, and has a cabin compartment filter on all applications. Refer to CONTROLS and FILTER, CABIN AIR for more information.

Scheme 2

All vehicles use an HVAC housing (4) that combines heating, ventilating and A/C capabilities into a single housing. Based upon the mode selected, conditioned air can exit the HVAC housing through one, or a combination of, the panel (2), defrost (1) and floor (5 and 3) outlets. Once the conditioned air exits the HVAC housing, it is further directed through molded plastic ducts to the air outlets within the vehicle interior. Refer to DISTRIBUTION for more information.

The A/C system uses a variable displacement compressor, R-134a refrigerant and an A/C expansion valve to meter the flow of refrigerant to the A/C evaporator. See PLUMBING for more information.

To maintain the performance level of the HVAC system, the engine cooling system must be properly maintained. The use of a bug screen is not recommended. Any obstructions in front of the radiator or A/C condenser will reduce the performance of the A/C and engine cooling systems. The engine cooling system includes the radiator, thermostat, radiator hoses and the engine coolant pump. See ENGINE COOLING SYSTEM for more information.

OPERATION

Note. Typical blend-air type HVAC system shown in illustration.

Scheme 3

The heating and A/C systems used in this vehicle are a single zone, blend-air type system. In this blend-air heating and A/C system, two blend-air doors (3) control the amount of conditioned air that is allowed to flow through, or around the heater core (2).

The system pulls outside (ambient) air through the fresh air intake (4) located at the cowl panel at the right side base of the windshield and into the air inlet housing, inside the passenger compartment. From there, the ambient air passes through the A/C evaporator (7) and is then directed either through or around the heater core. This is done by adjusting the position of the blend-air doors with the temperature control located on the A/C heater control in the instrument panel. Air flow is then directed out the floor outlets (8), instrument panel outlets (10) or the defroster outlets (1) in various combinations by adjusting the position of the mode-air doors (9 and 11) using the mode control located on the A/C heater control. The Automatic Temperature Control (ATC) system uses electric actuators to operate the blend and mode air doors. The Manual Temperature Control (MTC) system uses cables to operate the blend and mode air doors.

The velocity of the air flow out of the outlets can be adjusted with the blower speed control located on the A/C heater control.

The fresh air intake can be shut off by the Recirculation control, located on the A/C heater control. This will operate the electrically actuated recirculation-air door (5), which closes off the fresh air intake. With the fresh air intake closed, the conditioned air within the vehicle is pulled back into the HVAC housing through the recirculation air intake (6), located within the passenger compartment.

Note. It is important to keep the fresh air intake opening clear of debris. Leaf particles and other debris that is small enough to pass through the cowl opening screen can accumulate within the HVAC housing. The closed, warm, damp and dark environment created within the housing is ideal for the growth of certain molds, mildews and other fungi. Any accumulation of decaying plant matter that enters the housing with the fresh ambient air provides an additional food source for the fungal spores. If the air intake opening is not kept clear of debris, objectionable odors created by growing fungi and decaying plant matter, as well as excess debris, can be discharged into the passenger compartment during heater and A/C operation.

The A/C compressor can be engaged by pressing A/C (snowflake) button on the A/C heater control. When equipped, the A/C compressor will automatically engage when the mode control is set in any Mix to Defrost position. This will remove heat and humidity from the air before it is directed through or around the heater core.

The blend door actuator used in the Automatic Temperature Control (ATC) heating and A/C system is connected to the A/C heater control by a dedicated five-wire lead and connector of the HVAC wire harness. The blend door actuator can move the blend-air doors in two directions. When the A/C heater control pulls the voltage on one side of the motor connection high and the other connection low, the blend door actuator will move in one direction. When the A/C heater control reverses the polarity of the voltage to the motor, the blend door actuator moves in the opposite direction. Once the A/C heater control makes the voltage to both connections high or both connections low, the blend door actuator stops and will not move.

The blend door actuator contains a potentiometer, which the ATC A/C heater control uses to monitor the relative position of the blend-air doors. The A/C heater control learns the blend-air door stop positions during the calibration procedure and will store a diagnostic trouble code (DTC) for any problems it detects in the blend door actuator circuits. Refer to DIAGNOSIS AND TESTING .

The blend door actuator cannot be adjusted or repaired and must be replaced if inoperative or damaged.

The mode door actuator used in the Automatic Temperature Control (ATC) heating and A/C system is connected to the A/C heater control by a dedicated five-wire lead and connector of the HVAC wire harness. The mode door actuator can move the mode-air doors in two directions. When the A/C heater control pulls the voltage on one side of the motor connection high and the other connection low, the mode door actuator will move in one direction. When the A/C heater control reverses the polarity of the voltage to the motor, the mode door actuator moves in the opposite direction. Once the A/C heater control makes the voltage to both connections high or both connections low, the mode door actuator stops and will not move.

The mode door actuator contains a potentiometer, which the ATC A/C heater control uses to monitor the relative position of the mode-air doors. The A/C heater control learns the mode-air door stop positions during the calibration procedure and will store a diagnostic trouble code (DTC) for any problems it detects in the mode door actuator circuits. Refer to DIAGNOSIS AND TESTING .

The mode door actuator cannot be adjusted or repaired and must be replaced if inoperative or damaged.

The recirculation door actuator (1) is a reversible 12 volt Direct Current (DC) servo motor. The recirculation door actuator is located on the bottom of the HVAC air inlet housing, behind the instrument panel.

The recirculation door actuator is contained within a black molded plastic housing with an integral wire connector receptacle (4). Three mounting tabs (3) allow the actuator to be secured to the housing and output shaft (2) connects it to the recirculation air door.

The recirculation door actuator requires mechanical indexing to the recirculation air door.

The recirculation door actuator is connected to the A/C heater control or module (depending on heating and A/C system application) by a dedicated two-wire lead and connector of the HVAC wire harness. The recirculation door actuator can move the recirculation air door in two directions. When the A/C heater control or module pulls the voltage on one side of the motor connection high and the other connection low, the recirculation air door will move in one direction. When the A/C heater control or module reverses the voltage, the recirculation air door will move in the other direction. When the recirculation air door reaches its travel limit, the A/C heater control or module turns the voltage off.

When equipped with Automatic Temperature Control (ATC), the recirculation door actuator is diagnosed using a scan tool. Refer to DIAGNOSIS AND TESTING .

When equipped with Manual Temperature Control System (MTC). Refer to ACTUATOR, RECIRCULATION DOOR, DIAGNOSIS AND TESTING .

The recirculation door actuator cannot be adjusted or repaired and must be replaced if inoperative or damaged.

A blower motor power module is used on the Automatic Temperature Control (ATC) system, and allows the microprocessor-based A/C heater control to calculate and provide infinitely variable blower motor speeds based upon either manual blower switch input or the ATC programming.

The ATC blower motor control system uses a Pulse Width Modulated (PWM) circuit strategy. PWM voltage is applied to a comparator circuit which compares the PWM signal voltage to the blower motor feedback voltage. The resulting output drives the power module circuitry, which provides a linear output voltage to change or maintain the desired blower speed.

The blower motor power module is diagnosed using a scan tool. Refer to DIAGNOSIS AND TESTING .

The blower motor power module cannot be adjusted or repaired must be replaced if inoperative or damaged.

The ambient air temperature sensor is a variable resistor that operates on a 5 volt Direct Current (DC) reference signal sent by the Body Control Module (BCM). The ambient air temperature sensor is connected to the BCM through a two-wire lead and connector of the vehicle wire harness. The ambient air temperature sensor changes its internal resistance in response to changes in the outside air temperature, which either increases or decreases the reference signal voltage read by the BCM. The BCM converts and broadcasts the sensor data over the Controller Area Network (CAN) data bus, where it is read by the A/C-heater control, Powertrain Control Module (PCM) and other vehicle control modules.

The ambient air temperature sensor is diagnosed using a scan tool. Refer to the DIAGNOSTIC CODE INDEX .

The ambient air temperature sensor cannot be adjusted or repaired and must be replaced if inoperative or damaged. Refer to SENSOR, AMBIENT TEMPERATURE, REMOVAL .

Scheme 4

1. Disconnect and isolate the negative battery cable.
2. Disconnect the wire harness connector (1) from the ambient air temperature sensor (4).
3. Remove the push pin (2) that secures the ambient air temperature sensor to the radiator crossmember (3) and remove the sensor.

The evaporator temperature sensor monitors the surface temperature of A/C evaporator and supplies an input signal to the A/C heater module. The A/C heater module uses the evaporator temperature sensor input signal to optimize A/C system performance and to protect the A/C system from evaporator freezing. The evaporator temperature sensor will change its internal resistance in response to the temperatures it monitors and is connected to the A/C heater module through a sensor ground circuit and a 5 volt Direct Current (DC) reference signal circuit. As the temperature of the A/C evaporator decreases, the internal resistance of the evaporator temperature sensor decreases.

The A/C heater module uses the monitored voltage reading as an indication of evaporator temperature. The A/C heater module is programmed to respond to this input by requesting the Powertrain Control Module (PCM) to cycle the A/C clutch as necessary to optimize A/C system performance and to protect the A/C system from evaporator freezing.

When equipped with Automatic Temperature Control (ATC), the evaporator temperature sensor is diagnosed using a scan tool. Refer to DIAGNOSIS AND TESTING .

When equipped with Manual Temperature Control System (MTC). Refer to SENSOR, EVAPORATOR TEMPERATURE, DIAGNOSIS AND TESTING .

The evaporator temperature sensor cannot be adjusted or repaired and must be replaced if inoperative or damaged.

Four air outlet temperature sensors are used in the Automatic Temperature Control (ATC) heating and A/C system to measure the temperature of the conditioned air leaving the HVAC housing. Each air outlet temperature sensor is an electrical thermistor located within a molded plastic case.

Scheme 5

Each air outlet temperature sensor (2) is inserted into the mode case (1) near the top of the HVAC housing.

Each air outlet temperature sensor is connected to the vehicle electrical system through a separate wire lead and connector of the HVAC wire harness. The external location of the air outlet temperature sensors allow them to be removed or installed without removing the HVAC housing from the vehicle.

The air duct temperature sensors monitor the temperature of the conditioned air leaving the HVAC housing and supplies an input signal to the A/C heater control, when equipped with the Automatic Temperature Control (ATC) heating and A/C system. The air duct temperature sensors change their internal resistance in response to the temperatures they monitor. The air duct temperature sensors are connected to the ATC A/C heater control through a sensor ground circuit and a 5 volt Direct Current (DC) reference signal circuit. As the temperature of the conditioned air leaving the HVAC housing decreases, the internal resistance of the temperature sensor increases. As the temperature of the conditioned air leaving the HVAC housing increases, the internal resistance of the temperature sensor decreases.

The ATC A/C heater control uses the monitored voltage readings as an indication of air outlet temperature. The A/C heater control is programmed to respond to this and other inputs by adjusting the blend and the mode air door positions, and by cycling the A/C clutch on and off as necessary in order to automatically adjust the heating and A/C system to the operator temperature preference setting.

The air duct temperature sensors are diagnosed using a scan tool. Refer to DIAGNOSIS AND TESTING .

The air duct temperature sensors cannot be adjusted or repaired and must be replaced if inoperative or damaged.

Air is drawn from the passenger compartment by the aspirator motor and flows over the temperature thermistor. The thermistor changes resistance with air temperature. The Automatic Temperature Control (ATC) A/C-heater control receives the resistance signal over hard-wired circuits and calculates the temperature of the air in the passenger compartment. The ATC system then automatically makes adjustments to maintain the optimum passenger compartment comfort.

The in-car temperature sensor cannot be adjusted or repaired and must be replaced if inoperative or damaged.

The internal resistance in the A/C pressure transducer changes in response to the pressures in the high side of the A/C refrigerant system. The Powertrain Control Module (PCM) provides a five volt reference signal and a sensor ground to the A/C pressure transducer, and uses the output voltage of the transducer to determine refrigerant high-side pressure. The PCM is programmed to respond to this and other sensor inputs by controlling the operation of the A/C clutch and the radiator cooling fan to help optimize A/C system performance and to protect refrigerant system components from damage.

The A/C pressure transducer is diagnosed using a scan tool. Refer to the DIAGNOSTIC CODE INDEX .

The A/C pressure transducer cannot be adjusted or repaired and must be replaced if inoperative or damaged.

The Automatic Temperature Control (ATC) heating and A/C system uses two sun sensors to balance the system in response to side-to-side variations of sun light intensity. Passengers in sun and shadow require different functional settings because they experience very different temperatures. The sun sensor assembly provides data to the A/C heater control to help determine proper mode and blend-air door positions and blower motor speeds. The sun sensors are not thermistor type sensors, but rather photo diodes. For this reason the sun sensors responds to sun light intensity rather than temperature. The sun sensor assembly is also used to sense day and night conditions for automatic headlight control, if equipped.

The sun sensor is diagnosed using a scan tool. Refer to DIAGNOSIS AND TESTING .

The sun sensor assembly cannot be adjusted or repaired and must be replaced if inoperative or damaged.

The blower motor controls the velocity of air moving through the HVAC housing by spinning the blower wheel within the HVAC air inlet housing at the selected speed.

The Automatic Temperature Control (ATC) heating and A/C system uses an electronic blower motor power module to control blower motor speed. The power module uses a Pulse Width Modulated (PWM) input from the A/C heater control and a feedback signal from the blower motor to regulate the blower motor ground path. The blower motor receives battery current through the Body Control Module (BCM) whenever the ignition is in RUN, and the blower motor control is in any position except Off.

The blower motor control system is diagnosed using a scan tool. Refer to STANDARD PROCEDURE .

The blower motor and blower motor wheel are factory balanced and cannot be adjusted or repaired and must be replaced as an assembly if inoperative or damaged.

Possible causes of an inoperative blower motor include

1. Open fuse
2. Inoperative blower motor power module
3. Inoperative blower motor switch
4. Inoperative blower motor
5. Inoperative blower motor circuit wiring or wire harness connectors

The A/C receiver/drier performs a filtering action to prevent foreign material that may be in the refrigerant from contaminating the A/C expansion valve and the A/C compressor. Refrigerant enters the A/C receiver/drier as a high-pressure, low temperature liquid. Desiccant inside the A/C receiver/drier absorbs any moisture which may have entered and become trapped within the refrigerant system. In addition, during periods of high demand operation of the A/C system, the A/C receiver/drier acts as a reservoir to store surplus refrigerant.

The A/C receiver/drier is integral to the A/C condenser and has no serviceable parts.

The A/C receiver/drier cannot be repaired and the A/C condenser and receiver/drier must be replaced as an assembly, if the receiver/drier is leaking or damaged, or if an internal failure of the A/C compressor has occurred.

Scheme 6

This A/C compressor has a total displacement of 160 cubic centimeters (9.7 cubic inches) and a control valve (2) and a high pressure relief valve (3) located on the back cover. The A/C compressor is secured to the engine with three bolts.

A label identifying the use of R-134a refrigerant and ND-8 PAG oil is located on the A/C compressor.

Scheme 7

The A/C compressor (1) is a fixed displacement type compressor that uses an electromagnetic field coil and a clutch plate (3) to engage the drive pulley (4) to the compressor shaft.

The A/C compressor has the suction port (2) located on the top of the housing, and the discharge port (5) located on the cylinder head, at the rear of the compressor.

The A/C compressor has a label identifying the use of only R-134a refrigerant and ND-8 PAG oil.

The A/C condenser is located in the front of the engine compartment behind the front fascia. The A/C condenser is a heat exchanger that allows the high-pressure refrigerant gas being discharged by the A/C compressor to give up its heat to the air passing over the condenser fins (2), which causes the refrigerant to cool and change to a liquid state.

The A/C condenser is equipped with tapping blocks for the A/C refrigerant lines (1). The A/C condenser has an integral A/C receiver/drier (3).

When air passes through the fins of the A/C condenser, the high-pressure refrigerant gas within the A/C condenser gives up its heat. The refrigerant then condenses as it leaves the A/C condenser and becomes a high-pressure liquid. The volume of air flowing over the condenser fins is critical to the proper cooling performance of the A/C system. Therefore, it is important that there are no objects placed in front of the radiator grille openings at the front of the vehicle or foreign material on the condenser fins that might obstruct proper air flow. Also, any factory-installed air seals or shrouds must be properly reinstalled following radiator or A/C condenser service.

Note. Replacement of the refrigerant line O-ring seals and gaskets is required anytime a refrigerant line is disconnected. Failure to replace the rubber O-ring seals and metal gaskets could result in a refrigerant system leak.

The A/C condenser has no serviceable parts. The O-ring seals used on the connections are made from a special type of rubber not affected by R-134a refrigerant. The O-ring seals and gaskets must be replaced whenever a refrigerant line is disconnected from the A/C condenser.

The A/C condenser cannot be repaired and must be replaced if leaking or damaged.

Engine coolant is circulated through the heater hoses to the heater core at all times. As the coolant flows through the heater core, heat is removed from the engine and is transferred to the heater core tubes and fins. Air directed through the heater core picks up the heat from the heater core fins. The blend-air door allows control of the heater output air temperature by regulating the amount of air flowing through the heater core. The blower motor speed controls the volume of air flowing through the HVAC housing.

The heater core cannot be repaired and it must be replaced if inoperative, leaking or damaged.

Refrigerant system service ports are used to recover, recycle, evacuate, charge and test the A/C refrigerant system. Unique sizes are used on the two service ports for the R-134a refrigerant system to ensure the system is not accidentally contaminated with R-12 refrigerant or by service equipment used for R-12 refrigerant.

1. On the 1.4L engine, the high side service port is located on the A/C suction line in back of the engine on passenger side.
2. On the 1.4L engine, the low side service port is located on the A/C liquid line on the right front of engine by condenser.
3. On the 2.0L engine, the high side service port is located on the A/C suction/distribution line in front of the engine by the A/C compressor.
4. On the 2.0L engine, the low side service port is located on the A/C liquid line on the right front of engine by condenser.

Both the high side and low side A/C service port valve cores are serviceable.

Note. The protective cap aids in service port sealing and helps protect the refrigerant system from contamination. Remember to always reinstall the protective cap onto the service port when refrigerant system service is complete.

Each of the service ports has a threaded plastic protective cap installed over it from the factory. The service port caps are serviceable items.

Refrigerant enters the A/C evaporator from the A/C expansion valve as a low-temperature, low-pressure mixture of liquid and gas. As air flows over the fins of the A/C evaporator, the humidity in the air condenses on the fins, and the heat from the air is absorbed by the refrigerant. Heat absorption causes the refrigerant to boil and vaporize. The refrigerant becomes a low-pressure gas when it leaves the A/C evaporator.

Note. Replacement of the refrigerant line O-ring seals and gaskets is required anytime a refrigerant line is disconnected. Failure to replace the rubber O-ring seals and metal gaskets could result in a refrigerant system leak.

The A/C evaporator has no serviceable parts except for the O-ring seals. The O-ring seals used on the connections are made from a special type of rubber not affected by R-134a refrigerant.

The A/C evaporator cannot be repaired and must be replaced if leaking or damaged.

The A/C expansion valve controls the high-pressure, low temperature liquid refrigerant and converts it into a low-pressure, low-temperature mixture of liquid and gas, before it enters the A/C evaporator. A mechanical sensor in the A/C expansion valve monitors the temperature and pressure of the refrigerant leaving the A/C evaporator through the A/C suction line, and adjusts the orifice size at the liquid line port to let the proper amount of refrigerant into the evaporator to meet the vehicle A/C cooling requirements. Controlling the refrigerant flow through the A/C evaporator ensures that none of the refrigerant leaving the A/C evaporator is still in a liquid state, which could damage the A/C compressor.

Note. Replacement of the refrigerant line O-ring seals is required anytime a refrigerant line or A/C expansion valve is disconnected. Failure to replace the rubber O-ring seals may result in a refrigerant system leak.

The A/C expansion valve is factory calibrated and cannot be adjusted or repaired and must be replaced if inoperative or damaged.