Heating Output and Temperature Door Activation, Testing Requirements
Heating Output and Temperature Door Activation, Testing Requirements
• The coolant circuit has been bled according to specification.
• The engine is warm (the coolant temperature is higher than 80 °C (176 °F).
• Radiator and condenser are clean (if necessary clean)
• 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 for the A/C unit (in fresh air and recirculation mode) is not impaired by contamination or retrofitted components.
• Ensure that the air outlet from the rear footwell vents (under the front seats) is not blocked by floor mats or other objects.
• 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 event memory of the Climatronic control module (J255) , (and the Rear 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 A/C display control head if present) was checked using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
• The adaptation of the Climatronic control module (and the Rear A/C display control head if present) was checked using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
• 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".
• 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.
• Open all instrument panel vents and the vents in the rear center console.
• In the case of the Comfort version, open the vents in the B-pillars.
• The hood is closed.
• The engine is running.
• When the engine is running and the temperature selection is on "warm" on the Climatronic control module (i.e. "HI" is displayed on the "Comfort" version of the A/C system for the driver and passenger side in the Climatronic control module and the Multi Media Interface and on the Rear A/C display control head (E265) in the Display).
- The coolant shut-off valve (N82) is not activated.
- The heater coolant shut-off valve (N279) is not activated for vehicles with an auxiliary heater.
- The coolant pump (V50) is activated.
- The recirculation pump (V55) is activated for vehicles with an auxiliary heater.
• If the coolant shut-off valve (N82) is actuated, the passenger compartment is not heated. Check using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Function of the coolant shut-off valve, refer to => [ Coolant Shut-Off Valve (N82) ] Coolant Shut-Off Valve (N82).
• If the coolant shut-off valve does not open completely in the inactivated state, there may be a complaint regarding a lack of heating output.
• In vehicles without a parking heater, the coolant recirculation pump (V50) and the coolant shut-off valve (N82) are not always installed (depending on the equipment and the engine). Refer to => [ Integration of A/C Unit in Coolant Circuit ] Integration of A/C Unit In Coolant Circuit.
• If present, the Rear temperature selection potentiometer (G538) is set to "warm". 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.
When testing the heating output, it is helpful to display the following measured values of the Climatronic control module:
• Measured values of the following temperature sensor: Left/right vent temperature sensor (G150) / (G151) , left/right footwell vent temperature sensor (G261) / (G262) , evaporator vent temperature sensor (G263) ).
• Activation of the following components: fresh air blower (V2) , coolant fan (V7) , coolant fan 2 (V177).
• The activation of the A/C compressor regulator valve (N280) (compressor switch off controls and A/C compressor actual current).
• Coolant temperature and ambient temperature.
• The measured value of the A/C pressure/temperature sensor (G395) (refrigerant pressure).
Checking
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 - 4 - preselection "maximum speed".
If present, the rear temperature selection potentiometer (G538) - 1 - is set to "cold".
• The rear temperature selection potentiometer (G538) 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 - lights up.
• Preselection for the fresh air blower - 8 - 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 conditions (on-board voltage, etc.).
• Certain A/C system functions can be switched on and off via the MMI (Multi Media Interface) under the "A/C system" function in the "car"/"car systems" menu. The A/C system control can also be influenced via presettings in the MMI (Multi Media Interface) under the "A/C system" function in the "car"/"car systems" menu. Therefore, first check the presetting in the MMI in the case of a problem with these components. Refer to Infotainment/MMI operating instructions.
Functions with engine running
• For vehicles with the start stop system, the engine only runs potentially when an additional heat output is needed to reach the set temperature.
- 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 of Guided Fault Finding 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 switches to recirculation mode. Approximately 1 minute after the vehicle is started, the back pressure/fresh air door is closed, the recirculation door is opened, and the fresh air blower (V2) extracts the air from the passenger compartment below the instrument panel/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 value using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
If the requirements listed above are met, check the heating output and activation of the temperature doors: Basic version, refer to => [ Basic Vehicles - Heating Output and Activation of Temperature Doors, Checking ] Basic Vehicles - Heating Output and Activation of Temperature Doors, Checking, Comfort version, refer to => [ Comfort Vehicles - Heating Output and Activation of Temperature Doors, Checking ] Comfort Vehicles - Heating Output and Activation of Temperature Doors, Checking.