A/C Cooling Output, Testing Requirements
A/C Cooling Output, Testing Requirements
• Ambient temperature greater than 15 °C (59 °F)
• Radiator and condenser are clean (if necessary clean)
• The ribbed belt for the A/C compressor drive is OK and correctly tensioned and the belt pulley actually drives the A/C compressor (on vehicles with a 4 or 6 cylinder engine). Refer to => [ A/C Compressor Belt Pulley ] Description and Operation.
• The A/C compressor drive unit is mounted correctly, and the A/C compressor is actually driven (in vehicles with an 8 cylinder engine). Refer to => [ A/C Compressor Drive Unit Overview ] A/C Compressor Drive Unit Overview.
• All air ducts, covers and seals OK and properly installed.
• Air flow through dust and pollen filter not obstructed by dirt. Refer to=> [ Dust and Pollen Filter ] Service and Repair.
• Air intake of the A/C unit (in fresh air and recirculation mode) is not impaired by contamination or retrofitted components.
• In the case of the Comfort A/C system, the glove compartment cooling air guide is installed according to specification. Refer to=> [ Air Duct For Glove Compartment Cooling ] Air Duct For Glove Compartment Cooling (in the case of the Basic version, the glove compartment cooling connection is sealed).
• Vehicle not exposed to sunlight
• The engine is warm (the coolant temperature is higher than 80 °C (185 °F).
• The event memory of the Climatronic control module (J255) , (and the rear Climatronic A/C display control head (E265) if present) was checked and erased, the basic setting was performed, and the coding of the Climatronic control module (and the rear Climatronic A/C display control head) was checked using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
• The adaptation of the Climatronic control module (and the rear Climatronic A/C display control head if present) was checked using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
• In vehicles with a Basic A/C system: In the MMI (Multi Media Interface) the following is set via the "A/C system" function in the "Car"/"Car systems" menu for the regulation of the A/C system (if possible): air flow "medium climate control setting".
• In vehicles with a Comfort A/C system: In the MMI (Multi Media Interface) the following is set via the "A/C system" function in the "Car"/"Car systems" menu for the regulation of the A/C system (if possible): automatic recirculation "off", air flow "medium climate control setting" and footwell temperature "medium" (arrow pointing up).
• The various functions for the adjustment of the A/C system in the MMI (Multi Media Interface) (function "A/C" in the "Car" / "Car-System" menu) differ depending on the A/C system version, on the time period of production and on the vehicle version (not available for all versions). Refer to the Owner's manual.
• Currently no setting via the MMI is intended for vehicles in the USA version with the "Basic" A/C system. Refer to the Owner's manual.
• All instrument panel vents and the vents in the rear center console and in the B-pillar (in the Comfort version) are open.
• In the Comfort version, the glove compartment cooling vent (in the glove compartment) is closed.
• Ensure that the air outlet from the rear footwell vents (under the front seats) is not blocked by floor mats or other objects.
• The hood is closed.
• The engine is running.
Set the Basic version as follows on the Climatronic control module (J255) :
• "Auto" operating mode - the indicator lamp in the AUTO button - 1 - lights up.
• "Cold" temperature preselection - both knobs - 2, 5 - are set to "cold".
• The A/C compressor is switched on - the indicator lamp in the AC button - 6 - lights up.
• Fresh air blower knob - 4 - maximum speed.
If present, the rear temperature selection potentiometer (G538) - 1 - is set to "cold".
• The rear temperature selection potentiometer is only installed in vehicles with a certain country version of the Basic A/C system in the rear center console.
Set the Comfort version as follows on the Climatronic control module (J255) :
• "Auto" mode - the indicator lamps in both AUTO buttons - 2, 4 - illuminate.
• "Cold" temperature preselection via the knobs - 1, 5 - - "LO" displayed for the drive side and front passenger side in the display - 3 - of the Climatronic control module and in the Multi Media Interface display.
• The A/C compressor is switched on - the indicator lamp in the AC button - 9 - of the Climatronic control module lights up.
• Preselection for the fresh air blower - 7 - "maximum speed" - displayed in the display of Climatronic control module and in the display of the Multi Media Interface speed 10 or higher.
If present, the following is set on the rear A/C display control head (E265) :
• "Auto" mode - the indicator lamps in both AUTO buttons - 3, 6 - illuminate.
• "Cold" temperature preselection via the knobs - 2, 7 - - "LO" displayed for the left and right side in the display - 1 -.
• Preselection for the fresh air blower - 5 - "maximum speed" - display shows speed "5" or higher.
• The indicator lamps in the AUTO buttons go out when the fresh air blower speed is changed manually.
• The maximum possible fresh air blower speed depends on several environmental conditions (on-board voltage, etc.).
Functions with engine running
- The radiator fan ( radiator fan (V7) and radiator fan 2 (V177) ) run (activation and speed depend on pressure in coolant circuit and engine temperature).
• Depending on the version of the Climatronic control module (J255) , the coolant fan(s) ( coolant fan (V7) and coolant fan 2 (V177) ) is/are only switched on at a certain pressure in the refrigerant circuit (currently, at a pressure of approximately 9 bar). The activation of the coolant fan(s) is displayed in the "Read measured values" function using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
• Depending on the engine control module, the target speed and actual speed of the coolant fans (V7) and (V177) deviate from one another. Check using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- Fresh Air Blower runs at maximum speed.
• The maximum possible fresh air blower speed depends on several environmental conditions (vehicle system voltage, etc.).
- The A/C system goes in recirculation mode (approximately 1 minute after starting the engine, the back pressure/fresh air door is closed and the recirculation door is opened, the fresh air blower extracts the air from the passenger compartment below the instrument panel/behind the glove compartment).
• If one of these requirements is not met, check the event memory, perform the output diagnostic test mode and read out the relevant measured values using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.