Heating & Air Conditioning - Service Information: Overview Jeep Compass I рестайлинг 2

DESCRIPTION

An electronic Manual Temperature Control (MTC) single zone type heating-A/C system, electronic MTC heater-only system and an electronic Automatic Temperature Control (ATC) single zone type heating-A/C system are available on this model, depending on market.

To maintain the performance level of the Heating, Ventilation and Air Conditioning (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 before opening or attempting any service to the engine cooling system.

Scheme 2

The heating-A/C system combines A/C, heating, and ventilating capabilities in a single HVAC housing mounted within the passenger compartment beneath the instrument panel. All vehicles are equipped with a common HVAC housing that includes the following.

1. Blend-air door and actuator (1)
2. Evaporator temperature sensor (2) (when A/C equipped)
3. A/C evaporator (3) (when A/C equipped)
4. Mode-air doors (4)
5. Mode door actuator (5)
6. Recirculation-air door and actuator (6) (when A/C equipped)
7. Cabin air filter (7) (when equipped)
8. Blower motor (8)
9. Blower motor power module (9)
10. Heater core (10)

On heater-only systems, the A/C evaporator is omitted from the HVAC housing and is replaced with an air restrictor plate.

Note. An electric positive temperature coefficient (PTC) heater is used on vehicles when equipped with the 2.2L diesel engine. The PTC heater unit compensates for the lower engine coolant temperatures produced by the diesel engine. The PTC heater unit is mounted in the HVAC air distribution housing, downstream of the heater core. For more information. Refer to UNIT, HEATER, DESCRIPTION .

Based upon the system mode selected, conditioned air can exit the HVAC housing through one or a combination of the three main housing outlets: defrost, panel or floor. The defrost and panel outlets are located on the top of the HVAC air distribution housing and the floor outlets are located on each side of the distribution housing. Once the conditioned air exits the HVAC housing, it is further directed through molded plastic ducts to the various outlets within the vehicle interior. These outlets and their locations are as follows

1. Defroster Outlet - A single large defroster outlet is located in the center of the instrument panel, near the base of the windshield.
2. Side Window Demister Outlets - There are two side window demister outlets, one is located at each outboard end of the instrument panel top cover, near the belt line at the A-pillars.
3. Panel Outlets - There are four panel outlets in the instrument panel, one located near each outboard end of the instrument panel facing the rear of the vehicle and two located near the top of the instrument panel center bezel.
4. Front Floor Outlets - There are two front floor outlets, one located on each side the floor panel center tunnel behind the instrument panel.
5. Rear Seat Floor Outlets - There are two rear seat floor outlets, one located on each side of the floor panel near the front of each rear seat foot well.

OPERATION

The Manual Temperature Control (MTC) heating-A/C system, MTC heater-only system and the Automatic Temperature Control (ATC) heating-A/C system are blend-air type systems. In a blend-air system, a blend-air door controls the amount of conditioned air that is allowed to flow through, or around, the heater core. The temperature control determines the discharge air temperature by operating the blend door actuator, which moves the blend-air door. This design allows almost immediate control of output air temperature.

Scheme 3

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

The heating-A/C system pulls outside (ambient) air through the fresh air intake (4) located at the cowl panel at the base of the windshield and into the air inlet housing above the heating, ventilation and air conditioning (HVAC) housing. On models equipped with A/C, the air passes through the A/C evaporator (7). Air flow is then directed either through or around the heater core (2). This is done by adjusting the position of the blend-air door (3) with the temperature control located on the A/C-heater control in the instrument panel. Air flow is then directed out the floor outlet (8), instrument panel outlet (10) or the defroster outlet (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 mode control uses a control cable to operate the 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 pressing the Recirculation button 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.

The A/C compressor can be engaged by pressing the A/C (snowflake) button on the A/C-heater control. It 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 mode control on the A/C-heater control is used to direct the conditioned air to the selected system outlets.

The front and rear floor outlets receive airflow from the HVAC housing through the front and rear floor ducts. The front floor outlets are integral to the molded plastic front floor ducts, which are secured to each side of the HVAC housing. Two molded plastic rear seat ducts are attached to the two molded plastic rear floor ducts, which are secured to the rear of the HVAC housing. The rear seat ducts direct airflow beneath the carpet to the outlets located near the front of each rear seat foot well. None of the floor outlets can be adjusted.

The panel outlets receive airflow from the HVAC housing through the center air distribution duct and molded plastic panel outlet ducts. The airflow from each of the panel outlets is adjustable. A thumbwheel located at the bottom of each panel outlet grille is used to adjust a center diffuser that changes the airflow direction, and a knob on the outer edge of each panel outlet grille opens or closes a shutter to turn airflow on or off through that outlet.

The defroster outlet receives airflow from the HVAC housing through the molded plastic defroster duct, which is secured to the top of the instrument panel. The airflow from the defroster outlet is directed by fixed vanes in the defroster outlet grille and cannot be adjusted.

The side window demister outlets receive airflow from the HVAC housing through the defroster duct and molded plastic demister ducts. The airflow from the side window demister outlets is directed by fixed vanes in the demister outlet grilles and cannot be adjusted. The side window demister outlet grilles are integral to the instrument panel cover and direct air from the HVAC housing through the outlets on the top corners of the instrument panel. The demisters operate when the mode control is set in any Floor to Defrost position.

The blend door actuator is connected to the A/C-heater control through the vehicle electrical system by a dedicated two-wire lead and connector of the instrument panel wire harness. The blend door actuator can move the blend-air door 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-air door will move in one direction. When the A/C-heater control reverses the polarity of the voltage to the motor, the blend-air door moves in the opposite direction. Once the A/C-heater control makes the voltage to both connections high or both connections low, the blend-air door stops and will not move.

The A/C-heater control uses a pulse-count positioning system to monitor the operation and relative position of the blend door actuator and the blend-air door. 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 (1) for the heating-A/C system is a reversible, 12-volt Direct Current (DC) servo motor, which is mechanically connected to the mode-air doors. The mode door actuator is located on the right side of the HVAC air distribution housing.

The mode door actuator is contained within a black molded plastic housing with an integral wire connector receptacle (2). An output shaft with splines (3) connect it to mode door linkage and integral mounting tabs (4) allow the actuator to be secured to the air distribution housing. The mode door actuator does not require mechanical indexing to the mode-air doors, as it is electronically calibrated by the A/C-heater control.

The A/C-heater control must be recalibrated each time an actuator motor is replaced. Refer to STANDARD PROCEDURE .

The mode door actuator is interchangeable with the actuators for the recirculation and blend-air doors.

The mode door actuator is connected to the A/C-heater control through the vehicle electrical system by a dedicated two-wire lead and connector of the instrument panel wire harness. The mode door actuator can move the mode-air door 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-air door will move in one direction. When the A/C-heater control reverses the polarity of the voltage to the motor, the mode-air door moves in the opposite direction. Once the A/C-heater control makes the voltage to both connections high or both connections low, the mode-air door stops and will not move.

The A/C-heater control uses a pulse-count positioning system to monitor the operation and relative position of the mode door actuator and the mode-air door. 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 it must be replaced if inoperative or damaged.

The recirculation door actuator (1) is a reversible, 12 volt direct current (DC) servo motor, which is connected directly to the pivot shaft lever of the recirculation-air door. The recirculation door actuator is located on the right side of the HVAC air inlet housing.

The recirculation door actuator is contained within a black molded plastic housing with an integral wire connector receptacle (2), an output shaft with splines (3) connect it to the recirculation door and three integral mounting tabs (4) allow the actuator to be secured to the air inlet housing. The recirculation door actuator does not require mechanical indexing to the recirculation-air door, as it is electronically calibrated by the A/C-heater control.

The A/C-heater control must be recalibrated each time an actuator motor is replaced. Refer to STANDARD PROCEDURE .

The recirculation door actuator is interchangeable with the actuators for the blend and mode-air doors.

The recirculation door actuator is connected to the A/C-heater control through the vehicle electrical system by a dedicated two-wire lead and connector of the instrument panel wire harness. The recirculation door actuator can move the recirculation-air door 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 recirculation-air door will move in one direction. When the A/C-heater control reverses the polarity of the voltage to the motor, the recirculation-air door moves in the opposite direction. Once the A/C-heater control makes the voltage to both connections high or both connections low, the recirculation-air door stops and will not move.

The A/C-heater control uses a pulse-count positioning system to monitor the operation and relative position of the recirculation door actuator and the recirculation-air door. The A/C-heater control learns the recirculation-air door stop positions during the calibration procedure and will store a diagnostic trouble code (DTC) for any problems it detects in the recirculation door actuator circuits. Refer to DIAGNOSIS AND TESTING .

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

Note. ATC blower motor power module shown in illustration, MTC power module similar.

Scheme 4

A blower motor power module is used on this model when equipped with either the Automatic Temperature Control (ATC) heating-A/C system, or the Manual Temperature Control (MTC) heating-A/C system.

The blower motor power module is mounted to the bottom of the HVAC housing, on the passenger side of the vehicle. The blower motor power module consists of a molded plastic mounting plate (1) with an integral connector receptacle (2). Concealed behind the mounting plate is the power module electronic circuitry (3) and a finned aluminum heat sink (4). The blower motor power module is accessed for service from under the instrument panel.

The blower motor power module is connected to the vehicle electrical system through a dedicated lead and connector of the instrument panel wire harness. A second lead and connector of the instrument panel wire harness is connected to the blower motor.

On the Automatic Temperature Control (ATC) system, the blower motor power module 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.

On the Manual Temperature Control (ATC) system, the blower motor power module allows the microprocessor-based A/C-heater control to provide an infinite amount of blower motor speeds throughout its operating range, based upon blower switch input.

Both the ATC and MTC systems use 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 five volt reference signal sent by the Totally Integrated Power Module (TIPM). The ambient air temperature sensor is connected to the TIPM 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 TIPM. The TIPM converts and broadcasts the sensor data over the Controller Area Network (CAN) bus, where it is read by the Automatic Temperature Control (ATC) A/C-heater control, Powertrain Control Module (PCM), Cabin Compartment Node (CCN) and other vehicle control modules.

The ambient air temperature sensor is diagnosed using a scan tool. Refer to DTC 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 5

The evaporator temperature sensor measures the temperature of the conditioned air downstream of the A/C evaporator. The evaporator temperature sensor is an electrical thermistor (1) mounted on the end of a molded plastic housing (2) that is inserted into the driver side of the HVAC housing near the coldest point of the A/C evaporator. The evaporator temperature sensor is retained in the HVAC housing by two integral retaining tabs (3) and is connected to the vehicle electrical system by use of a wire lead and connector (4) with two terminals.

The evaporator temperature sensor monitors the surface temperature of A/C evaporator and supplies an input signal to the A/C-heater control. The A/C-heater control 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 control through sensor ground circuit and a 5-volt 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 control uses the monitored voltage reading as an indication of evaporator temperature. The A/C-heater control is programmed to respond to this input by requesting the powertrain control module (PCM) or the engine control module (ECM) (depending on engine application) to adjust the compressor swash plate angle as necessary to optimize A/C system performance and to protect the A/C system from evaporator freezing. Refer to COMPRESSOR, A/C, OPERATION .

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

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

The infrared sensor detects thermal radiation emitted by the driver and front passenger seat occupants and surroundings and converts its data into a linear Pulse Width Modulated (PWM) output signal which is read by the Automatic Temperature Control (ATC) A/C-heater control. The ATC A/C-heater control uses the infrared sensor data as one of the inputs necessary to automatically control the interior cabin temperature levels. By using thermal radiation (surface temperature) measurement, rather than an air temperature measurement, the ATC heating-A/C system is able to adjust itself to the comfort level as perceived by the occupants. This allows the ATC system to compensate for other ambient conditions affecting comfort levels, such as solar heat gain or evaporative heat loss.

The ATC system logic responds to the infrared sensor message by calculating and adjusting the air flow temperature and air flow rate needed to properly obtain and maintain the selected comfort level temperature of the occupants. The A/C-heater control continually monitors the infrared sensor circuits, and will store Diagnostic Trouble Codes (DTCs) for any problem it detects.

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

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

The A/C pressure transducer monitors the pressures in the high side of the refrigerant system through its connection to a fitting on the A/C discharge line. The internal resistance of the A/C pressure transducer changes in response to the pressures it monitors. The Totally Integrated Power Module (TIPM) provides a five volt reference signal and a sensor ground to the A/C pressure transducer. The TIPM then monitors the output voltage of the transducer on a sensor return circuit to determine refrigerant pressure and sends a message to the Powertrain Control Module (PCM) or Engine Control Module (ECM) (depending on engine application) over the Controller Area Network (CAN) C BUS. The PCM/ECM is programmed to respond to this and other sensor inputs by controlling the operation of the swash plate within the A/C compressor and the radiator cooling fan to help optimize A/C system performance and to protect the system components from damage. The PCM adjusts the swash plate to nearly a zero degree angle (low compressor displacement) when high side pressure rises above 3130 kPa (454 psi) and readjusts the swash plate to a greater angle (higher compressor displacement) when high side pressure drops below 1999 kPa (290 psi). The A/C pressure transducer also reduces the swash plate angle if the high side pressure drops below 200 kPa (29 psi) and will increase the swash plate angle when the high side pressure rises above 234 - 262 kPa (34 - 38 psi). When the refrigerant pressure rises above 1655 kPa (240 psi) the PCM will actuate the cooling fan.

A Schrader-type valve in the A/C discharge line fitting permits the A/C pressure transducer to be removed or installed without disturbing the refrigerant in the A/C system.

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

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

Note. LHD model shown, RHD model similar.

Scheme 6

All models use a common HVAC housing assembly. The HVAC housing assembly is mounted within the passenger compartment and consists of three separate housings

1. HVAC housing - The HVAC housing (1) is mounted to the dash panel behind the instrument panel and contains the A/C evaporator, when equipped with A/C. The HVAC housing consists of an upper and a lower housing that are attached together and has mounting provisions for the air inlet housing, air distribution housing, blower motor and blower motor resistor or power module (depending on application).
2. Air distribution housing - The air distribution housing (2) is mounted to the rear of the HVAC housing and contains the heater core, blend-air and mode-air doors and door linkage.
3. Air inlet housing - The air inlet housing (3) is mounted to the passenger side end of the HVAC housing. When equipped with A/C, the air inlet housing contains the recirculation-air door and recirculation door actuator.

The heating-A/C system is a blend-air type system. The blend-air door controls the amount of conditioned air that is allowed to flow through, or around, the heater core.

The A/C system is designed for the use of a non-CFC, R-134a refrigerant and uses an A/C evaporator to cool and dehumidify the incoming air prior to blending it with the heated air. The discharge air temperature is controlled by an electric blend door actuator, which moves the blend-air door. This allows an almost immediate control of the output air temperature of the system. The electric mode door actuator operates the mode-air doors, which direct the flow of the conditioned air out the various air outlets, depending on the mode selected. The blower motor controls the velocity of air flowing through the HVAC housing assembly by spinning the blower wheel within the HVAC housing at the selected speed by use of a blower motor resistor or power module (depending on application). When equipped with A/C, an electric recirculation door actuator operates the recirculation-air door, which closes off the fresh air intake and recirculates the air already inside the vehicle. The electric door actuators, blower motor resistor or power module (depending on application) and the blower motor are connected to the vehicle electrical system by the instrument panel wire harness.

The air distribution housing must be removed from the HVAC housing and disassembled for service of the blend-air and mode-air doors. The air inlet housing must be removed from HVAC housing and disassembled for service of the recirculation-air door. The HVAC housing must be removed from the vehicle and disassembled for service of the A/C evaporator.

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.

Both the Manual Temperature Control (MTC) heating-A/C system and the Automatic Temperature Control (ATC) heating-A/C system have 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. On both systems, the blower motor receives battery current through the Totally Integrated Power Module (TIPM) whenever the ignition switch is in the Run position, and the blower motor control is in any position except Off.

The blower motor can be accessed for service from underneath the instrument panel and is diagnosed using a scan tool. Refer to DIAGNOSIS AND TESTING .

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

Possible causes of an inoperative blower motor include

1. Open fuse
2. Inoperative blower motor power module
3. Inoperative A/C-heater control
4. Inoperative blower motor
5. Inoperative blower motor circuit wiring or wire harness connectors

Note. A/C condenser for late model year gasoline engine with automatic transaxle shown in illustration, Other models similar.

Scheme 7

The A/C condenser (1) is a heat exchanger that allows the high-pressure refrigerant gas being discharged from A/C compressor to give up its heat to the air passing over the condenser fins, which causes the refrigerant flowing through the condenser to cool and change to a liquid state. The A/C condenser is located at the front of the engine compartment, behind the grille.

The A/C condenser has tapping blocks for the A/C refrigerant lines (2) and the integral automatic transmission cooler (4), when equipped.

Early model year gasoline engine equipped vehicles with automatic transaxle have the A/C receiver/drier mounted to the right front frame rail. Refer to DRIER, A/C RECEIVER, DESCRIPTION . Late model year gasoline engine equipped vehicles with automatic transaxle have the A/C receiver/drier (3) mounted to the left end of the A/C condenser.

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.

Note. LHD model shown in illustration, RHD model similar.

Scheme 8

The heater core (1) for the heating-A/C system is mounted within the HVAC air distribution housing, which is located behind the instrument panel. The heater core is a heat exchanger made of rows of tubes with fins and is positioned within the air distribution housing so that only the selected amount of air entering the housing passes through the heater core before it is distributed through the heating-A/C system ducts and outlets. One end of the heater core is fitted with a tank (2) that includes the fittings for the heater core tubes (3).

The heater core can only be serviced by removing the HVAC housing from the vehicle.

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.

The A/C receiver/drier is part of the high-side of the A/C system. The A/C receiver/drier stores any unused refrigerant, filters and helps remove moisture from the refrigerant, and retains any refrigerant vapor that may leave the A/C condenser, until it becomes a liquid. The A/C receiver/drier is located on the right front frame rail or on the A/C condenser, depending on engine and transaxle application.

Scheme 9

On all early model vehicles, the A/C receiver/drier (1) is mounted to the right front frame rail (4). On late model vehicles, only the gasoline and diesel engine models with manual or Constant Velocity Transaxle (CVT) have the A/C receiver/drier mounted to the frame rail. Late model gasoline engine equipped vehicles with automatic transaxle have the A/C receiver/drier mounted to the A/C condenser.

The A/C liquid line (2) and jumper line (3) are attached to the A/C receiver/drier and the connections are sealed by use of metal gaskets with rubber O-ring seals.

Scheme 10

On late model gasoline engine equipped vehicles with automatic transaxle, the A/C receiver/drier (1) is mounted to the left end of the A/C condenser (2) and must be replaced with the condenser as an assembly.

The A/C receiver/drier performs a filtering action to prevent foreign material in the refrigerant from contaminating the A/C expansion valve. 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.

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 receiver/drier has no serviceable parts except for the O-ring seals and gaskets. 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 the A/C receiver/drier is disconnected.

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

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 or expansion valve 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 refrigerant. The O-ring seals must be replaced whenever the A/C expansion valve is removed from the A/C evaporator.

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 from the A/C liquid line 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 is disconnected from the expansion valve, or if the expansion valve is removed. 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.

The Positive Temperature Coefficient (PTC) heater unit dissipates 1 kW of electrical power through four heating bars. The Engine Control Module (ECM) and the Totally Integrated Power module (TIPM) operate the two relays for the PTC heater unit. The PTC heater unit is split into two "banks". Each bank is driven separately based on alternator load. This allows for lower in-rush current and optimum battery charging. After a bank has been turned on, another bank can only be turned on 10 seconds after the previous. On average, the PTC banks are not switched more than 25 times for each vehicle start. The electrical power output is between 900-1050 W.

The control system for the PTC heater unit is diagnosed using a scan tool. Prior to replacing a PTC heater unit, check for any Diagnostic Trouble Codes (DTCs) related to the ECM, TIPM and heating-A/C system. See the appropriate Diagnostic Information.

The PTC heater unit cannot be adjusted or repaired and must be replaced if inoperative or damaged.