Heating Output and Temperature Door Activation, Testing Requirements

Heating Output and Temperature Door Activation, Testing Requirements

• Coolant circuit has been bled according to specifications.

• 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.

• The air intake for the front A/C unit (in fresh air and recirculation mode) is not impaired by contamination or subsequently installed components.

• Ensure that the air outlet from the rear footwell vents (under the front seats) is not blocked by floor mats or other objects.

• The air duct for glove compartment cooling is installed in the glove compartment as specified, refer to => [ Air Duct For Glove Compartment Cooling ] Air Duct For Glove Compartment Cooling.

• 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.

• The following is set in the MMI (Multi Media Interface) via the "A/C system" function in the "car"/"car systems" menu for the regulation of the A/C system: automatic recirculation off, air flow center and footwell temperature medium (arrow pointing up).

• All instrument panel vents, the B-pillar vents, and the vents in the rear center console are open.

• The hood is closed.

• The engine is running.

• With the engine running and the temperature preselection warm (display HI) on the Climatronic control module (and the rear A/C display control head if present) and in the Multi Media Interface display.

• The coolant shut-off valve (N82) (the heater coolant shut-off valve) is not activated.

• The coolant recirculation pump (the recirculation pump of the parking heater) is not activated.

• If in vehicles with a coolant shut-off valve (not installed in all vehicles) or with a heater coolant shut-off valve this component is activated, the passenger compartment is not heated, refer to => [ Coolant Shut-Off Valve (N82) ] Coolant Shut-Off Valve (N82) and the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

• If the coolant shut-off valve/heater coolant shut-off valve does not open completely in the unactivated state, there may be a complaint regarding a lack of heating output.

• In vehicles with a parking heater as optional equipment, no coolant shut-off valve and no coolant recirculation pump are installed. In these vehicles, the parking heater components assume this function (the heater coolant shut-off valve and the recirculation pump).

• On vehicles with the optional equipment parking heater the recirculation pump for the parking heating actuated and the heater coolant shut-off valve not actuated.

When testing the heating output, it is helpful to display the following measured values of the Climatronic control module:

• The measured values of the following temperature sensor (left vent temperature sensor, right vent temperature sensor, Left footwell vent temperature sensor, right footwell vent temperature sensor, evaporator vent temperature sensor).

• The measured value of the rear intake air temperature sensor (only in a vehicle without a rear A/C display control head)

• The activation of the following components ( fresh air blower (V2) , rear fresh air blower (V80) , coolant fan (V7) , coolant fan 2 (V177) )

• The activation of the following components (if present, depending on the equipment and engine type coolant recirculation pump/ recirculation pump (V55) , coolant shut-off valve/heater coolant shut-off valve)

• The activation of the A/C compressor regulator valve (N280) (compressor shutoff conditions and actual compressor current)

• The coolant temperature and the ambient temperature.

• The measured value of the A/C pressure/temperature sensor (G395) (coolant pressure).

• For vehicles where there is also the version with the rear air distribution housing, there is a rear Climatronic A/C display control head (E265) installed. The air temperature and the air volume calculated and regulated by the Climatronic control module (J255) is also influenced by the setting on the rear Climatronic A/C display control head. However, only the temperature is adjustable for this rear Climatronic A/C display control head and there is only an AUTO button, refer to => [ Rear A/C Control Head (E265) ] Rear A/C Control Head (E265).

Checking

Set the following on the Climatronic control module:

• Auto mode (the indicator lamps in both AUTO buttons illuminate).

• Temperature preselect cold for the driver's and passenger's side (display LO for the driver's and passenger's die in the A/C Control Head display and in the Multi Media Interface display).

• The A/C compressor is switched on (the indicator lamp in the AC button comes on).

• Preselection for the fresh air blower (the fresh air blower (V2) and the rear fresh air blower) maximum speed (shown in the display of the Climatronic control module and in the display of the Multi Media Interface speed 10 or higher).

Set the following on the rear A/C display control head if present:

• Auto mode (the indicator lamps in both AUTO buttons illuminate).

• Temperature preselection cold (display LO for the left and right sides).

• Preselection for the rear fresh air blower maximum speed.

• The indicator lamps in the AUTO buttons of the Climatronic control module (and the rear A/C display control head) go out when the fresh air blower speed is changed manually.

• The maximum possible fresh air blower speed depends on several conditions (coolant temperature, vehicle voltage, etc.)

• For vehicles where there is also the version with the rear air distribution housing, there is a rear Climatronic A/C display control head (E265) installed for specific markets). The air temperature and the air volume calculated and regulated by the Climatronic control module (J255) is additionally influenced by the setting on the rear Climatronic A/C display control head. However, only the temperature is adjustable for this rear Climatronic A/C display control head and there is only an AUTO button, refer to => [ Rear A/C Control Head (E265) ] Rear A/C Control Head (E265).

- Check that for vehicles with the diesel engine, the activation and functionality of the auxiliary heater is OK.

• In vehicles with a diesel engine, an auxiliary air heater control module (J604) with an auxiliary heater heating element (Z35) is installed. Refer to => [ Auxiliary Electric Heater (Z35) ] Description and Operation.

• If there is a complaint regarding insufficient heating output at low outside temperatures in vehicles with a diesel engine, check the settings in the MMI for the auxiliary heater and the activation and function of the auxiliary heater.

• 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:

- The radiator fan (coolant fan and coolant fan 2) run (activation and speed depend on pressure in coolant circuit and engine temperature).

• Depending on the version of the Climatronic control module, the coolant fan(s) (coolant fan and coolant fan 2) are only switched on starting at a certain pressure in the coolant circuit (currently starting at a pressure of approximately 9 bar (130.5 psi)). The activation of the coolant fan(s) is displayed in the "read measured values" function of the Guided Fault Finding using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function

- The Fresh Air Blower runs with maximum speed (10 or greater).

- The rear fresh air blower runs at maximum speed.

• The maximum possible fresh air blower speed depends on several conditions (coolant temperature, vehicle voltage, etc.)

- The front A/C system switches to recirculation mode. Approximately 1 minute after the vehicle is started, 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/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 above mentioned requirements are fulfilled:

• Heating output and activation of the temperature doors => [ Heat Output and Temperature Door Activation Tests ] Heat Output and Temperature Door Activation Tests.