Specified Values For The Refrigerant Circuit Pressures

The temperature of the air downstream of the evaporator, the current A/C compressor speed and the refrigerant pressure on the high pressure side are displayed as a measured value by the Climatronic Control Module -J255- display and control head. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for A/C System and the Battery Regulation.

If a high cooling output is required (for example, a high outside temperature and the blower speed set on high), then the A/C compressor will not bring the pressure on the low pressure side to the required value (for example, for a certain time after turning on the A/C). The A/C compressor is not actuated at the maximum specified speed (of approximately 8500/min) on a stationary or slow moving vehicle (up to a speed of approximately 45km/h) (the A/C compressor speed is limited to approximately 5000/min). After a vehicle reaches a speed of more than approximately 45 km /h, the limit for the maximum permissible A/C compressor speed is lifted. At a A/C compressor speed of 5000/min, a high outside temperature and a high fresh air blower speed (inefficient environmental controls), the A/C compressor output (the delivery volume) is no longer sufficient to reduce the pressure on the low pressure side to the target value. To check the A/C compressor control under these conditions, for example, the fresh air blower is controlled only with approximately 40% of the maximum voltage, check the pressures at a lower fresh air blower speed. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for A/C System and the Battery Regulation and the BATTERY (vehicle-specific repair information).

Under unfavorable conditions (very high ambient temperatures, high humidity), pressure on high-pressure side may increase to max. 29 bar (421 psi).

The specified A/C compressor speed is displayed as a measured value by the Climatronic Control Module -J255- display and control head. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for A/C System.

The measured high pressure by the A/C Pressure/Temperature Sensor -G395- or by the Refrigerant Circuit Pressure Sensor -G805- is displayed as a measured value by the Climatronic Control Module -J255- display and control unit. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding  " function for the air conditioner and TRANSMISSION CONTROL MODULE SAFETY FUNCTIONS (vehicle-specific repair information).

The low pressure settles depending on the A/C compressor speed and the control characteristic of the expansion valve within the compressor output range in tolerance range (1.5 to 2.3 bar (22 to 33 psi) positive pressure).

The target speed for the A/C compressor must be greater than 1500 /min for this test.

In setting "maximum cooling output" the target speed is regulated to approximately 4000 up to 5000 /min. This value is vehicle-specific and is displayed as a measured value by the Climatronic Control Module -J255- display and control head. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for A/C System and Battery Regulator.

At absolute pressure, 0 bar/psi corresponds to absolute vacuum. Normal ambient pressure corresponds to 1 bar (14.5 psi) absolute pressure. On the scales of most pressure gauges, 0 bar/psi corresponds to an absolute pressure of 1 bar (14.5 psi) (can be seen from -1 bar (-14.5 psi) mark below 0). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for A/C System and BATTERY (vehicle-specific repair information).

If, on a vehicle with two evaporators (one in the A/C unit and one for cooling the high voltage components, for example, in the battery cooling module or the high voltage battery heat exchanger), the measured temperature on one evaporator corresponds to the specified value or the specified value falls short, but does not reach the required specified value on the other evaporator, the following adjustment is performed: the responsible control module (the Battery Regulation Control Module -J840- or the Climatronic Control Module -J255-) activates the Electrical A/C Compressor -V470- with increased speed via various other control modules (for example, the Electric Drive Power and Control Electronics -JX1- and the A/C Compressor Control Module -J842-). Thereby increasing the A/C cooling output and decreasing the pressure on the low pressure side as well as the evaporator temperature. If the specified value for the temperature falls short at one evaporator, the relevant control module (for example the Battery Regulation Control Module -J840- or the Climatronic Control Module -J255-) activates the installed shut-off valves (Hybrid Battery Refrigerant Shut-Off Valve 1 -N516-, Heater and A/C Unit Refrigerant Cut-Off Valve -N541-, Hybrid Battery Refrigerant Shut-Off Valve 2 -N517- or High Voltage Battery Heater Core Refrigerant Cut-Off Valve -N542-) so that the evaporator which is too cold is no longer supplied with refrigerant. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for A/C System and refer to appropriate System Wiring Diagram and Repair Information (vehicle-specific repair information).

Since the evaporator for cooling the high voltage components output (in the battery cooling module and in the high voltage battery heat exchanger) is noticeably smaller than the evaporator output in the A/C unit, the required target temperature may still be reached in the evaporator for cooling the high voltage battery with too little refrigerant in the refrigerant circuit, but the target temperature in the A/C unit evaporator will no longer be attainable (even though the A/C compressor is activated with increased air conditioner speed).

If no fault is found with this malfunction, clean the refrigerant circuit (flush using refrigerant R134a. Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING), WITH REFRIGERANT R134A ; or blow through using compressed air and nitrogen. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH COMPRESSED AIR AND NITROGEN ). One of these malfunctions may arise due to a constriction or a blockage in the refrigerant circuit.

Checking the measured value for the sensor for the Evaporator Vent Temperature Sensor -G263- and if equipped the Temperature Sensor before Hybrid Battery Evaporator - G756- and the Temperature Sensor after Hybrid Battery Evaporator - G757- as well as the A/C compressor activation via the respective control modules (for example the A/C Compressor Control Module -J842- from the Battery Regulation Control Module -J840- or from the A/C system display and control, the Climatronic Control Module -J255-). Refer to the Vehicle Diagnostic Tester in "Guided Fault Finding  " Function for A/C System and the Battery Regulation and appropriate System Wiring Diagram Information.

If there is an error in the measured value of the evaporator vent temperature sensor -G263- (or for example the temperature sensor before hybrid battery evaporator -G756- or the temperature sensor before hybrid battery evaporator -G757-) this can lead to problems in the cooling output or the air conditioner can freeze up. Refer to the Vehicle Diagnostic Tester "Guided Fault Finding  " function for the air conditioner and the Battery Regulation.

If A/C system operation is not OK i.e. after repeating the test, for example after replacing expansion valve (reinstalling the old expansion valve), clean the refrigerant circuit (flush using the refrigerant R134a. (Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING), WITH REFRIGERANT R134A .); or blow through using the compressed air and nitrogen. (Refer to REFRIGERANT CIRCUIT, FLUSHING WITH COMPRESSED AIR AND NITROGEN ). Then replace the A/C compressor and receiver/dryer or dryer cartridge.

With a malfunction on one of the temperature sensors, the evaporator may ice up even though the quantity of refrigerant in the circuit is OK.

If the expansion valve in the A/C unit evaporator (or for example the hybrid battery refrigerant shut-off valve 1 -N516- / heater and a/c unit refrigerant cut-off valve -N541-) is malfunctioning (permanently closed or does not open sufficiently), the A/C compressor is actuated to maximum output and the low pressure drops to value in graph or below (compressor draws off refrigerant from low-pressure side). As the refrigerant cannot flow via the expansion valve, the cooling output is not attained, high pressure may also not increase or only increase slightly due to the absence of energy. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for the A/C System and the Battery Regulation and GENERAL REPAIR INFORMATION (vehicle-specific repair information).

The evaporator in the A/C system has considerably more output than the evaporator for cooling the high voltage components (for example in the battery cooling module or in the high voltage battery heat exchanger). The shut-off valve (for example the Hybrid Battery Refrigerant Shut-Off Valve 2 -N517- on the expansion valve in the battery cooling module or the High Voltage Battery Heater Core Refrigerant Cut-Off Valve - N542-) are depending on the cooling version of the Traction Battery - A2- / Hybrid Battery Unit -AX1- (hybrid battery) is currently activated from and to a specific battery temperature by the Battery Regulation Control Module -J840- or from the air conditioning display and control unit, the Climatronic Control Module -J255-, so that the energy does not or only slightly increases via the evaporator for cooling high voltage components (in the battery cooling module or in the high voltage battery heat exchanger). Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " for the function for the A/C system and battery control and GENERAL REPAIR INFORMATION .

On a vehicle with a battery cooling module, to cool the Traction Battery -A2- (hybrid battery), the Hybrid Battery Refrigerant Shut-Off Valve 2 -N517- is currently activated by the Battery Regulation Control Module -J840- after a specific battery temperature is reached. If the A/C system driver is not already activated at this time, the Electrical A/C Compressor -V470- is activated via the A/C Compressor Control Module -J842- by the battery regulation control module -J840-. The temperature of the air in front of and behind the evaporator in the battery cooling module is determined by the battery regulation control module -J840-. If it can be determined that there is insufficient cooling, the information will be saved in the battery regulation control module -J840-. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for the A/C System, the A/C Compressor and the Battery Regulation.

On a vehicle with a battery cooling module, the temperature of the air (as well as the evaporator cooling output) in the battery cooling module is determined via the installed temperature sensor (it currently cannot be measured using a thermometer while operating) and may only be checked using the Guided Fault Finding  . Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for the A/C System, the A/C Compressor and the Battery Regulator.

On a vehicle with a battery cooling module pay attention to the additional notes SPECIFIED VALUES FOR THE REFRIGERANT CIRCUIT PRESSURES => If no fault is found with this malfunction, clean the refrigerant circuit (flush using refrigerant R134a. .

On a vehicle with a high voltage battery charger the Climatronic Control Module -J255- control head no longer activates the High Voltage Battery Heater Core Refrigerant Cut-Off Valve -N542- from a certain temperature to cool the high voltage components (for example the Traction Battery -A2-, the High Voltage Battery Charger Control Module -J1050- etc.) the from a specific temperature (the -N542- open when deenergized). If the A/C system driver is not already activated at this time, the Electrical A/C Compressor -V470- is activated via the A/C Compressor Control Module -J842- from the Climatronic control module -J255- control head. So that the high voltage battery is actually cooled by the coolant, additionally further components of the circuit must be activated (for example the Engine Coolant Circulation Pump 2 -V178- and the Solenoid Valve 1 -N88-) and coolant must be flowing through the high voltage battery heat exchanger. If it can be determined that there is insufficient cooling, the information will be saved in various control modules. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for the A/C System, the A/C Compressor and the Battery Regulator and OVERVIEW - REFRIGERANT CIRCUIT .

If no fault is found with this malfunction, clean the refrigerant circuit (flush using refrigerant R134a. Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING), WITH REFRIGERANT R134A ; or blow through using compressed air and nitrogen. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH COMPRESSED AIR AND NITROGEN ). One of these malfunctions may arise due to a constriction or a blockage in the refrigerant circuit.

If the A/C system functionality is not OK when the test is repeated, replace the expansion valve and receiver/dryer (and the hybrid battery refrigerant shut-off valve 1 -N516- / heater and a/c unit refrigerant cut-off valve -N541-, if equipped).

With this malfunction, evaporator may ice up although the quantity of refrigerant in circuit is OK.

If the expansion valve in the A/C unit evaporator or the hybrid battery refrigerant shut-off valve 1 -N516- / heater and a/c unit refrigerant cut-off valve -N541- is malfunctioning (permanently closed or does not open sufficiently), the A/C compressor is actuated to maximum output and the low pressure drops to specification or below (compressor draws off refrigerant from low-pressure side). As no (or too little) of the refrigerant can flow via the expansion valve (the hybrid battery refrigerant shut-off valve 1 -N516- / heater and a/c unit refrigerant cut-off valve -N541-), the cooling output is not attained and the high pressure may also not increase or only increase slightly due to the absence of energy. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for the A/C System and the Battery Controls. and GENERAL REPAIR INFORMATION (vehicle-specific repair information).

In a vehicle with a battery cooling module if the expansion valve on the evaporator in the battery cooling module is faulty (or if the functionality or activation of the Hybrid Battery Refrigerant Shut-Off Valve 2 -N517- is malfunctioning), constantly closed or does not open enough, then the A/C compressor is likewise activated with the maximum output (the required temperatures in the battery cooling module are not attained). The pressure on the low pressure side only falls to the target value or lower when there is no cooling output is requested at the same time in the A/C unit (the hybrid battery refrigerant shut-off valve 1 -N516- is activated and is closed). The A/C compressor extracts the refrigerant from the low pressure side from both evaporators). Since, however, no refrigerant can flow over the expansion valve in the A/C system (the hybrid battery refrigerant shut-off valve 1 -N516-) and the cooling output in the battery cooling module is not attained (there is a malfunction in the battery cooling module), the electrical A/C compressor will be activated with a higher speed. Since, however, none of the refrigerant can flow through, the pressure on the low pressure side falls below the target value. In addition, the high pressure may never or only slightly increase, due to the absence of energy. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for the A/C System and the Battery Controls. and GENERAL REPAIR INFORMATION (vehicle-specific repair information).

If on a vehicle with a high voltage battery heat exchanger the refrigerant line to the high voltage battery heat exchanger the installed restrictor is plugged or in this line the installed High Voltage Battery Heater Core Refrigerant Cut-Off Valve -N542- is faulty, continuously closed or does not open wide enough, then the A/C compressor is likewise activated with the maximum output (the required temperatures in the battery cooling module are not attained). The pressure on the low pressure side only falls to the target value or lower when there is no cooling output is requested at the same time in the A/C unit (the heater and a/c unit refrigerant cut-off valve -N541- is activated and is closed). The A/C compressor extracts the refrigerant from the low pressure side from both evaporators). Since, however, no refrigerant can flow over the expansion valve in the A/C system (the heater and a/c unit refrigerant cut-off valve -N541-) and the cooling output in the high voltage battery heat exchanger is not attained, the electrical A/C compressor will be activated with a higher speed. Since, however, none of the refrigerant can flow through, the pressure on the low pressure side falls below the target value. In addition, the high pressure may never or only slightly increase, due to the absence of energy. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for the A/C System and the Battery Controls. and GENERAL REPAIR INFORMATION (vehicle-specific repair information). The same applies when a malfunction occurs in the coolant circuit which installed in the high voltage battery heat exchanger (for example the Engine Coolant Circulation Pump 2 -V178- or the Solenoid Valve 1 - N88- are not correctly activated or are faulty). The high Voltage Battery Heat Exchanger is cooled but the cooled coolant does not reach the high voltage components. Refer to Coolant Fan Control Module J293 and OVERVIEW - REFRIGERANT CIRCUIT .

Since the evaporator for cooling the high voltage components output is noticeably smaller than the evaporator output in the A/C unit, the required target temperature may still be reached in the evaporator for cooling the high voltage battery with too little refrigerant in the refrigerant circuit, but the target temperature in the A/C unit evaporator will no longer be attainable (even though the A/C compressor is activated with increased air conditioner speed).

If there is too much refrigerant oil in the circuit, the compressor must be drained (flushed) and the receiver/dryer or dryer cartridge must be replaced. After cleaning the refrigerant circuit (flushing with refrigerant R134a. Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING), WITH REFRIGERANT R134A ; or blowing through using compressed air and nitrogen. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH COMPRESSED AIR AND NITROGEN ), the correct quantity of refrigerant oil is filled into the circuit (in the A/C compressor). Refer to APPROVED REFRIGERANT OILS AND CAPACITIES .

It is not initially necessary to clean the refrigerant circuit (flush using refrigerant R134a. (Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING), WITH REFRIGERANT R134A .); or blow through using compressed air and nitrogen, (Refer to REFRIGERANT CIRCUIT, FLUSHING WITH COMPRESSED AIR AND NITROGEN .) when this problem occurs since normally there is only a small quantity of moisture in the system which can be removed by lengthy evacuation.

If a problem involving moisture in refrigerant circuit only occurs after a lengthy operating period or only infrequently (low pressure drops below specification and evaporator ices up), it is sufficient to replace the dryer installed in receiver/dryer (adjust quantity of refrigerant oil). Refrigerant circuit is then to be evacuated for at least three hours.

With this malfunction, evaporator may ice up although the quantity of refrigerant in circuit is OK.

Likewise, the refrigerant circuit may become iced if there is a malfunction on the Evaporator Vent Temperature Sensor -G263- or / and on the Temperature Sensor after Hybrid Battery Evaporator -G757-. Also note for this malfunction the measured value for the evaporator vent temperature sensor -G263- and for the temperature sensor after hybrid battery evaporator -G757 - (for vehicles with a battery cooling module). Refer to Vehicle Diagnostic Tester in the Function "Guided Fault Finding  " for the A/C System. Refer to GENERAL REPAIR INFORMATION (vehicle-specific repair information).

For the malfunction "high pressure normal, low pressure too low", note the following: With this malfunction, evaporator in the air conditioner may ice up although the quantity of refrigerant in circuit is OK.

If there is a fault in the A/C compressor (the A/C compressor is activated by the A/C Compressor Control Module -J842- at too high of a speed), it is not necessary to clean the refrigerant circuit (with refrigerant R134a, (Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING), WITH REFRIGERANT R134A .) or blow through it with compressed air and nitrogen. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH COMPRESSED AIR AND NITROGEN .). In this case, it is sufficient to replace the A/C compressor (observe quantity of refrigerant oil in A/C compressor and if necessary adjust).

If on a vehicle with a battery cooling module the expansion valve for the A/C unit evaporator or the expansion valve for the evaporator in the battery cooling module) is faulty (permanently closed or does not open sufficiently), the A/C compressor is also actuated to maximum output and the pressure on the low pressure side drops to value in graph or below (compressor draws off refrigerant from low-pressure side). Since the refrigerant cannot flow via the faulty expansion valve, the cooling output in the downstream evaporator is not attained and the high pressure may also not increase or only increase slightly due to the absence of energy. The A/C compressor may thereby be activated with a higher speed since the required cooling output is not attained in an evaporator. The same goes for the functionality and the activation of the Hybrid Battery Refrigerant Shut-Off Valve 1 -N516- or the Hybrid Battery Refrigerant Shut-Off Valve 2 -N517- if they are faulty. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for the A/C System and the Battery Controls and GENERAL REPAIR INFORMATION (vehicle-specific repair information).

If on a vehicle with a high Voltage Battery Heat Exchanger the expansion valve for the evaporator in the air conditioner is fault (permanently closed or does not open sufficiently) or the restrictor in the refrigerant line to the high voltage battery heat exchanger is plugged, the A/C compressor is also actuated to maximum output and the pressure on the low pressure side drops to value in graph or below (compressor draws off refrigerant from low-pressure side). Since the refrigerant cannot flow via the faulty expansion valve or the plugged restrictor, the cooling output in the downstream evaporator is not attained and the high pressure may also not increase or only increase slightly due to the absence of energy. The A/C compressor may thereby be activated with a higher speed since the required cooling output is not attained in an evaporator. The same goes for the functionality and the activation of the Heater and A/C Unit Refrigerant Cut-Off Valve -N541-, the High Voltage Battery Heater Core Refrigerant Cut-Off Valve -N542- or one of the components installed in the coolant circuit for the high voltage components (for example the Engine Coolant Circulation Pump 2 -V178- or the Solenoid Valve 1 -N88-.Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " and OVERVIEW - REFRIGERANT CIRCUIT and OVERVIEW - REFRIGERANT CIRCUIT (vehicle-specific repair information).

Check the measured value of the Evaporator Vent Temperature Sensor -G263- (and if equipped the measured value of the Temperature Sensor before Hybrid Battery Evaporator - G756- and the Temperature Sensor after Hybrid Battery Evaporator -G757-) as well as the activation of the A/C compressor from the Battery Regulation Control Module -J840- or from the Climatronic Control Module -J255- A/C control head. If the measured values for the evaporator vent temperature sensor -G263- (or temperature sensor before hybrid battery evaporator -G756-, for the temperature sensor after hybrid battery evaporator -G757-) or the activation of the A/C compressor is defective, the evaporator may ice up or the requirements for the cooling output will not be attained. ReferTo "Guided Fault Finding  " Function for the A/C System and GENERAL REPAIR INFORMATION (vehicle-specific repair information).

This fault may also be caused by too much refrigerant oil in the circuit. Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.

If on a vehicle with a battery cooling module the expansion valve for the A/C unit evaporator or the expansion valve for the evaporator in the battery cooling module) is faulty (permanently closed or does not open sufficiently), the A/C compressor is also actuated to maximum output and the pressure on the low pressure side drops to value in graph or below (compressor draws off refrigerant from low-pressure side). Since the refrigerant cannot flow via the faulty expansion valve, the cooling output in the downstream evaporator is not attained and the high pressure may also not increase or only increase slightly due to the absence of energy. The A/C compressor may thereby be activated with a higher speed since the required cooling output is not attained in an evaporator. The same goes for the functionality and the activation of the Hybrid Battery Refrigerant Shut-Off Valve 1 -N516- or the Hybrid Battery Refrigerant Shut-Off Valve 2 -N517- if they are faulty. Refer to Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function and OVERVIEW - REFRIGERANT CIRCUIT (vehicle-specific repair information).

If on a vehicle with a high Voltage Battery Heat Exchanger the expansion valve for the evaporator in the air conditioner is fault (permanently closed or does not open sufficiently) or the restrictor in the refrigerant line to the high voltage battery heat exchanger is plugged, the A/C compressor is also actuated to maximum output and the pressure on the low pressure side drops to value in graph or below (compressor draws off refrigerant from low-pressure side). Since the refrigerant cannot flow via the faulty expansion valve or the plugged restrictor, the cooling output in the downstream evaporator is not attained and the high pressure may also not increase or only increase slightly due to the absence of energy. The A/C compressor may thereby be activated with a higher speed since the required cooling output is not attained in an evaporator. The same goes for the functionality and the activation of the Heater and A/C Unit Refrigerant Cut-Off Valve -N541-, the High Voltage Battery Heater Core Refrigerant Cut-Off Valve -N542- or one of the components installed in the coolant circuit for the high voltage components (for example the Engine Coolant Circulation Pump 2 -V178- or the Solenoid Valve 1 -N88-.Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding  " Function for the A/C System, OVERVIEW - REFRIGERANT CIRCUIT and OVERVIEW - REFRIGERANT CIRCUIT (vehicle-specific repair information).

Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.

If, for example, the expansion valve in the evaporator in the air conditioner is faulty (permanently open), the evaporator temperature (in the A/C unit) is no longer regulated such that only refrigerant leaves the evaporator in a gaseous state. Under certain usage conditions, liquid droplets may then be drawn in by the compressor and cause noise (liquid cannot be compressed).

If there is too much refrigerant oil in the circuit, the compressor must be drained and the receiver/dryer must be replaced. After cleaning the refrigerant circuit (for flushing with refrigerant R134a. Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING), WITH REFRIGERANT R134A ), fill the refrigerant circuit with the correct quantity of refrigerant. Refer to APPROVED REFRIGERANT OILS AND CAPACITIES .