Heating & Air Conditioning - Service Information: Overview RAM Pickup 2500

DESCRIPTION

A Manual Temperature Control (MTC) single zone or an Automatically Temperature Control (ATC) dual zone heating-air conditioning system is available on this model.

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

Note. Dual zone system shown in illustration. Single zone system similar.

All vehicles are equipped with a common HVAC housing (1). The system combines air conditioning, heating, and ventilating capabilities in a single unit housing mounted within the passenger compartment under the instrument panel. The HVAC housing includes

1. Blend-air door(s) and actuator(s) (2 and 10)
2. Heater core (3)
3. A/C evaporator (4)
4. Recirculation-air door and actuator (5)
5. Evaporator temperature sensor (6)
6. HVAC wire harness (7)
7. Blower motor (8)
8. Blower motor resistor or power module (9)
9. Mode-air doors and actuators (11)

Based upon the system and 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 the panel outlets are located on the top of the housing and, the floor outlet is located on the bottom of the 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 - Four defroster outlets are located in the instrument panel top cover, 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 above each side of the floor panel center tunnel near the dash panel.
5. Rear Outlets - On Crew Cab models there are two outlets located at the rear of the center front seat.

OPERATION

Both the Manual Temperature Control (MTC) single zone heating-A/C system and the Automatic Temperature Control (ATC) dual zone heating-A/C system are blend-air type systems. In a blend-air heating-A/C system, a blend-air door controls the amount of conditioned air that is allowed to flow through, or around the heater core. In the available dual zone system, two blend-air doors are used to provide completely independent side-to-side temperature control of the discharge air. The temperature control(s) determines the discharge air temperature(s) by operating the blend door actuator(s), which move the blend-air door(s). This design allows almost immediate control of output air temperature(s).

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 and 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(s) (3) with the temperature control(s) 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 temperature and mode control uses electrical actuators to operate the 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 defroster outlet receives airflow from the HVAC housing through the molded plastic defroster duct, which connects to the HVAC housing defroster outlet. The airflow from the defroster outlets is directed by fixed vanes in the defroster outlet grilles and cannot be adjusted. The defroster outlet grilles are integral to the instrument panel top cover.

The side window demister outlets receive airflow from the HVAC housing through the molded plastic defroster duct and two 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. The demisters direct air from the HVAC housing through the outlets located on the top corners of the instrument panel. The demisters operate when the mode control knob is positioned in the floor-defrost and defrost-only settings. Some air may be noticeable from the demister outlets when the mode control is in the bi-level to floor positions.

The panel outlets receive airflow from the HVAC housing through a molded plastic main panel duct, center panel duct and two end panel ducts. The two end panel ducts direct airflow to the left and right instrument panel outlets, while the center panel duct directs airflow to the two center panel outlets. Each of these outlets can be individually adjusted to direct the flow of air.

The floor outlets receive airflow from the HVAC housing through the floor distribution duct. The front floor outlets are integral to the molded plastic floor distribution duct, which is secured to the bottom of the housing. The floor outlets cannot be adjusted.

Note. It is important to keep the 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 provides an additional food source for fungal spores, which enter the housing with the fresh intake-air. Excess debris, as well as objectionable odors created by decaying plant matter and growing fungi can be discharged into the passenger compartment during heater-A/C operation if the air intake opening is not kept clear of debris.

The A/C system is designed for non-CFC, R-134a refrigerant and uses an A/C expansion valve to meter the flow of refrigerant through the A/C evaporator. The A/C evaporator cools and dehumidifies the incoming air prior to blending it with the heated air. An evaporator temperature sensor is used to supply evaporator temperature input to the A/C-heater control to maintain minimum evaporator temperature and prevent evaporator freezing. The Powertrain Control Module (PCM) or Engine Control Module (ECM), depending on engine application, cycles the A/C clutch off and on as necessary to protect the A/C system from evaporator freezing and optimize A/C system performance.

The blend door actuators are connected to the A/C-heater control through the vehicle electrical system by a dedicated two-wire lead and connector of the HVAC wire harness. The blend door actuator(s) can move the blend-air door(s) 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.

When 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(s) and the blend-air door(s). 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.

The blend door actuators are diagnosed using a scan tool. Refer to DIAGNOSIS AND TESTING for ATC or DIAGNOSIS AND TESTING for MTC .

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

The mode door actuators are connected to the A/C-heater control through the vehicle electrical system by dedicated two-wire leads and connectors of the HVAC wire harness. The mode door actuators can move the defrost-air door and the panel/floor-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.

When 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 actuators and the mode-air doors. The A/C-heater control learns the mode-air door stop positions during the Actuator Calibration procedure and will store a Diagnostic Trouble Code (DTC) for any problems it detects in the mode door actuator circuits.

The mode door actuators are diagnosed using a scan tool. Refer to DIAGNOSIS AND TESTING for ATC or DIAGNOSIS AND TESTING for MTC .

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

The recirculation door actuator is connected to the heater-A/C control module through the vehicle electrical system 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 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 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 Actuator Calibration procedure and will store a Diagnostic Trouble Code (DTC) for any problems it detects in the recirculation door actuator circuits.

The recirculation door actuator is diagnosed using a scan tool. Refer to DIAGNOSIS AND TESTING for ATC or DIAGNOSIS AND TESTING for MTC .

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

The blower motor power module is connected to the vehicle electrical system through a dedicated lead and connector of the HVAC wire harness. A second lead and connector of the HVAC wire harness is connected to the blower motor. The blower motor power module allows the microprocessor-based automatic temperature control (ATC) A/C-heater control to calculate and provide infinitely variable blower motor speeds based upon either manual blower switch input or the ATC programming using a pulse width modulated (PWM) circuit strategy.

The 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 for ATC or DIAGNOSIS AND TESTING for MTC .

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

The blower motor resistor is connected to the vehicle electrical system through a dedicated wire lead and connector of the HVAC wire harness. The blower motor resistor has multiple resistor wires, each of which will reduce the current flow through the blower motor to change the blower motor speed.

The blower motor control for the heating-A/C system directs the ground path for the blower motor through the correct resistor wire to obtain the selected speed. With the blower motor control in the lowest speed position, the ground path for the blower motor is applied through all of the resistor wires. Each higher speed selected with the blower motor control applies the blower motor ground path through fewer of the resistor wires, increasing the blower motor speed.

The blower motor resistor cannot be adjusted or repaired and must be replaced if inoperative or damaged.

The ambient air temperature sensor is a variable resistor that operates on a 5-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) IHS bus, where it is read by the ATC A/C-heater control, Powertrain Control Module (PCM) or Engine Control Module (ECM), depending on engine application, and other vehicle control modules.

The ambient air temperature sensor is diagnosed using a scan tool or Refer to DIAGNOSIS AND TESTING for ATC or DIAGNOSIS AND TESTING for MTC .

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

Scheme 4

Note. Cutaway of HVAC housing shown in illustration for clarity.

The evaporator temperature sensor (1) is an electrical thermistor located within a molded plastic case that is inserted into the top of the HVAC housing (2) to measure the temperature of the conditioned air downstream of the A/C evaporator (3). Two terminals within the connector receptacle connect the sensor to the vehicle electrical system through a wire lead and connector of the HVAC wire harness.

The external location of the evaporator temperature sensor allows the sensor to be removed or installed without disturbing the refrigerant in the A/C system.

The evaporator temperature sensor monitors the temperature of the conditioned air downstream of the 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 a 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 Engine Control Module (ECM), depending on engine application, to cycle the A/C clutch as necessary to optimize A/C system performance and to protect the A/C system from evaporator freezing.

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

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

Scheme 5

Note. Illustration shown in illustration with instrument panel removed for clarity.

1. Disconnect and isolate the negative battery cable.
2. Remove the glove box from the instrument panel. Refer to «GLOVE BOX, Instrument Panel , Removal»(ref-457777-S40043193292012030200000) .
3. Remove the storage bin from the instrument panel. Refer to «BIN, Instrument Panel , Removal»(ref-457777-S24923993642012030200000) .
4. Disconnect the HVAC wire harness (2) from the evaporator temperature sensor (1) located on top of the HVAC housing (3).
5. Pull the evaporator temperature sensor upward and forward and remove the sensor from the HVAC housing.

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 for ATC or DIAGNOSIS AND TESTING for MTC .

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

Scheme 6

1. Disconnect and isolate the negative battery cable.
2. Remove the overhead console (1) and place it on a workbench. Refer to «CONSOLE, Overhead, Front , Removal»(ref-457777-S16882044832012030200000) .
3. Remove the screw (3) that secures the infrared sensor (2) to the overhead console and remove the sensor.

The ATC dual-zone heating-A/C system uses two sun sensors to balance the system in response to side-to-side variations in 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 for ATC or DIAGNOSIS AND TESTING for MTC .

The sun sensor assembly 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 A/C refrigerant system through its connection to a fitting on the A/C discharge line and its internal resistance changes in response to the pressures it monitors. The Powertrain Control Module (PCM) or Engine Control Module (ECM), depending on engine application, provides a five volt reference signal and a sensor ground to the A/C pressure transducer, then monitors the output voltage of the transducer on a sensor return circuit to determine refrigerant pressure. The PCM/ECM 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 the system components from damage. The PCM/ECM will disengage the A/C clutch when high side pressure rises above 3172 kPa (460 psi) and re-engage the clutch when high side pressure drops below 1999 kPa (290 psi). The A/C pressure transducer will also disengage the A/C clutch if the high side pressure drops below 193 kPa (28 psi) and will re-engage the clutch when the high side pressure rises above 234 kPa (34 psi). If the refrigerant pressure rises above 1655 kPa (240 psi), the PCM/ECM will actuate the cooling fan. The A/C pressure transducer signal to the PCM/ECM also prevents the A/C clutch from engaging when ambient temperatures are below about 10° C (50° F), due to the pressure/temperature relationship of the refrigerant.

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 or refer to DIAGNOSIS AND TESTING for ATC or DIAGNOSIS AND TESTING for MTC .

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

The blower motor is used to control the velocity of air moving through the HVAC housing assembly by spinning the blower wheel within the air inlet housing at the selected or programmed speed (depending on control system application).

On the Manual Temperature Control (MTC) heating-A/C system, blower motor speed is controlled by regulating the path to ground through the blower control switch and the blower motor resistor. With the Automatic Temperature Control (ATC) heating-A/C system, blower motor speed is controlled by an electronic blower motor power module, which uses a pulse width modulated 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 will operate whenever the ignition switch is in RUN and the blower motor control is in any position except Off. The blower motor receives battery current through the Totally Integrated Power Module (TIPM) whenever the ignition switch is in RUN.

The blower motor can be accessed for service from underneath the instrument panel.

Note. The blower motor is supplied with a 12V feed from the TIPM whenever the ignition switch is in RUN. Due to an open circuit condition within the blower motor control switch the TIPM is UNABLE to detect an OPEN circuit for the blower motor.

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

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 resistor
3. Inoperative blower motor switch
4. Inoperative blower motor
5. Inoperative blower motor circuit wiring or wire harness connectors

Note. Gasoline engine model A/C condenser shown in illustration. Diesel engine model similar.

Scheme 7

The A/C condenser (1) is located at the front of the engine compartment, behind the grille. 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, which causes the refrigerant to cool and change to a liquid state.

The A/C condenser has integral mounting tabs, integral A/C receiver/drier (2), tapping blocks for the A/C refrigerant lines (3 and 4) and a tapping block for the integral automatic transmission cooler (5), when equipped.

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 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 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(s) 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 must be replaced if restricted, leaking or damaged.

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

The high side service port is located on the A/C liquid line. The low side service port is located on the A/C suction line. Both the high side and low side A/C service port valve cores are serviceable.

Each of the service ports has a threaded plastic protective cap installed over it from the factory. After servicing the refrigerant system, always reinstall both of the service port caps.

An A/C pressure transducer is mounted on the A/C discharge line to monitor the high side A/C system pressures. Refer to TRANSDUCER, A/C Pressure , Description .

Note. Gasoline engine model A/C condenser shown in illustration. Diesel engine model similar.

Scheme 8

The A/C receiver/drier (1) stores unnecessary refrigerant, filters the refrigerant, helps remove moisture from the refrigerant and retains any refrigerant vapor that may leave the A/C condenser (2) until it becomes a liquid. The A/C receiver/drier is on the high-side of the A/C system and is located on the left side of the A/C condenser.

The A/C receiver/drier is integral to the A/C condenser and must be replaced with the condenser as an assembly.

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 must be replaced if the receiver/drier is leaking or damaged, or if an internal failure of the A/C compressor has occurred. Refer to CONDENSER, A/C , Removal .

Scheme 9

The A/C evaporator (1) for the heating-A/C system is located within the HVAC housing, behind the instrument panel. The A/C evaporator and insulator (2) are positioned in the HVAC housing so that all air entering the housing must pass over the evaporator fins before it is distributed through the heating-A/C system ducts and outlets. However, air passing over the evaporator fins will only be conditioned when the A/C compressor is engaged and circulating refrigerant through the A/C evaporator. The A/C expansion valve is attached directly to the evaporator inlet and outlet ports (3) and the connections are sealed by O-rings.

The A/C evaporator can be serviced by removing and partially disassembling the HVAC housing.

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 R-134a 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.