Pressures, Checking, Vehicles With Electrically Driven A/C Compressor (Vehicles With High-Voltage System): Notes
High voltage is extremely dangerous.
The high-voltage system is under high voltage. Electrocution can cause death or very serious personal injury.
-- Individuals with electronic/medical life and health sustaining machines in or on their person cannot perform any work on high-voltage systems. Life and health sustaining machines are for example pain killer pumps, implanted defibrillators, pacemakers, insulin pumps, and hearing aids.
-- Have the high-voltage system de-energized by a qualified person.
There is a risk of injury due to the engine starting unexpectedly.
On electric and hybrid vehicles an active ready mode is difficult to identify. Parts of the body can be pinched or pulled.
-- Switch off the ignition.
-- Place the ignition key outside of the vehicle interior.
Risk of damaging the high-voltage cables.
Misuse can damage the insulation of high-voltage cables or high-voltage connectors.
-- Never support objects on the high-voltage cables and the high-voltage connectors.
-- Never support tools on the high-voltage cables and the high-voltage connectors.
-- Never sharply bend or kink the high-voltage cables.
-- When connecting pay attention to the coding of the high-voltage connectors.
- For all procedures on vehicles with a high-voltage system, pay attention to the additional warnings for these vehicles. Refer to WARNINGS WHEN WORKING ON VEHICLES WITH HIGH VOLTAGE SYSTEM .
- If procedures are necessary near components of the high-voltage system, "visually inspect the high-voltage components and lines for damage". Refer to PERFORMING A VISUAL INSPECTION OF DAMAGE TO HIGH VOLTAGE COMPONENTS AND CABLES .
- If work on the high-voltage system components is necessary, de-energize the high-voltage system. Refer to the appropriate service information.
The following steps using the A/C service station (checking pressures) on the refrigerant circuit can only be performed while the drive ready mode is active. If necessary, restart the high-voltage system.
-- Charge the vehicle batteries, for example, using the :VAS5904 in the battery support mode to minimize the number of automatic starts during the test- and measuring procedures while the ready mode is active. Refer to BATTERY, CHARGING and the appropriate service information. .
-- For testing and measurement procedures that require the ready mode to be active or the ignition to be switched on, the selector lever must be in the "P" position and the parking brake must be activated. The required tools must be placed so that they do not come into contact with any rotating engine components and they must also not go near the rotating components when the engine is running.
Also move the selector lever into position "P" and activate the parking brake for testing and measuring procedures that require the ignition to be on, but do not require the ready mode to be active.
The ready mode appears in the Instrument Cluster Control Module -J285- via the "power meter". Refer to the Owner's Manual.
Activate and deactivate the ready mode. Refer to the Owner's Manual (watch the display in the Instrument Cluster Control Module -J285- while doing this).
-- On vehicles with a high-voltage system, switch off (deactivate) the "auxiliary climate control" function. Refer to the Owner's Manual and Infotainment/MMI Operating Manual.
-- Switch off the ignition.
If a malfunction occurs at only one evaporator in vehicles with two evaporators (one evaporator in the A/C unit and the other in the battery cooling module or in the high-voltage battery heat exchanger), also check pressures in the refrigerant circuit, are these OK? Check the line connection between the evaporator in question and the exit of line connection at distribution point of refrigerant lines (for constriction or blockage, for example in the refrigerant line restrictor to the high-voltage battery heat exchanger). If no malfunction can be detected, discharge the refrigerant circuit and charge it with the specified refrigerant quantity. Then check the pressures and A/C system cooling output again; if the malfunction occurs again, check/replace the following components: if the complaint is only occurs at the evaporator in the A/C unit, the shut-off valve is prematurely switched by the evaporator (for example Hybrid Battery Refrigerant Shut-Off Valve 1 -N516- or the Heater and A/C Unit Refrigerant Shut-Off Valve -N541-). This component is open when it is not activated and allows the refrigerant to flow through. Replace the expansion valve on the evaporator in the A/C unit, if no fault can be found on the Hybrid Battery Refrigerant Shut-Off Valve 1 -N516- /Heater and A/C Unit Refrigerant Shut-Off Valve -N541-. If a malfunction occurs only on the evaporator for the cooling the high-voltage components (for example in the battery cooling module), check the activation of the Hybrid Battery Refrigerant Shut-Off Valve 2 -N517- on the evaporator expansion valve in the battery cooling module (it is closed when it is not activated and does not allow the refrigerant to flow through). If the complaint only occurs at the high-voltage battery heat exchanger, check the High-Voltage Battery Heater Core Refrigerant Shut-Off Valve -N542- (it is open when it is not activated and allows the refrigerant to flow through) and the restrictor installed in the refrigerant line. Refer to Refrigerant Circuit .
-- With the ignition switched off, check the pressures in the refrigerant circuit (using the A/C service station). Refer to REFRIGERANT CIRCUIT, CHECKING PRESSURE WITH SERVICE STATION .
The pressures with the ignition turned off meet the specifications.
-- Charge the vehicle batteries, for example, using the Battery Charger :VAS5904 in the battery support mode to minimize the number of automatic starts during the test- and measuring procedures while the ready mode is active. Refer to BATTERY, CHARGING and the appropriate service information. .
Also move the selector lever into position "P" and activate the parking brake for testing and measuring procedures that require the ignition to be on, but do not require the ready mode to be active.
The engine must not be running when checking the pressures in the refrigerant circuit on vehicles with a high-voltage system.
The ready mode appears in the Instrument Cluster Control Module -J285- via the "power meter". Refer to the Owner's Manual.
Activate the ready mode (and observe the display in the Instrument Cluster Control Module -J285-). Refer to the Owner's Manual.
-- Activate the drive ready mode. Refer to the Owner's Manual.
-- Switch the A/C system on.
-- Observe the pressure gauge of the service station.
The activation of the electrically driven A/C compressor occurs from the vehicle electrical system. The engine speed does not have any effect on the A/C cooling output.
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).
The activation of the electrically driven A/C compressor can be monitored by the Guided Fault Finding using the Vehicle Diagnostic Tester in the "Guided Fault Finding" Function for A/C System and the Battery Regulation.
Pressures must be measured at the service connections; the component location for these connections are vehicle-specific. Refer to Refrigerant Circuit .