Comfort Vehicles - Heating Output and Activation of Temperature Doors, Checking
Comfort Vehicles - Heating Output and Activation of Temperature Doors, Checking
Test requirements are met. Refer to => [ Heating Output and Temperature Door Activation, Testing Requirements ] Heating Output and Temperature Door Activation, Testing Requirements
- Close the engine hood.
- Close the doors, the engine hood, the windows, the sunroof and the rear lid.
- Open all instrument panel vents and the vents in the rear center console.
- Open the vent in the B-pillars.
- Close the vent for glove compartment cooling in the glove compartment.
- Turn on the ignition and prepare the drive ready mode, the engine starts automatically as needed (for vehicles with a start-stop system).
- Start the engine.
Set the following 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.
• By pressing the SYNC button - 10 - on the Climatronic control module, the settings for the front driver side are applied to the front passenger side and also on the rear A/C display control head.
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.
• Set the air flow direction via the button - 4 - and the knobs - 2, 7 - to "center console vent" and "vent in the B-pillars" - displayed in the display of the rear A/C display control head.
• The indicator lamps in the both AUTO buttons go out when the air flow direction and/or the fresh air blower speed is changed manually.
• The maximum possible fresh air blower speed depends on several environmental conditions (on-board voltage, etc.).
• The instrument panel vents, the B-pillar vents, and the vents in the rear center console are open.
- Select the "Read measured values" function of the A/C system on the Climatronic control module using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- Let the A/C system run for several minutes with maximum cooling output.
• The A/C compressor is switched on - the indicator lamp in the AC button comes on.
- Compare the measured value of the Evaporator vent temperature sensor (G263) to the measured values of the Left vent temperature sensor (G150) , Right vent temperature sensor (G151) , Left footwell vent temperature sensor (G261) and Right footwell vent temperature sensor (G262).
• Target values: The measured values of the temperature sensors (after the heat exchanger) Left vent temperature sensor, Right vent temperature sensor, Left footwell vent temperature sensor, Right footwell vent temperature sensor and the Evaporator vent temperature sensor may only be a maximum of 9° C greater than the value of the Evaporator vent temperature sensor after 5 minutes.
• As a result of the design of the A/C unit and the air guide in the vehicle, a certain increase in air temperature always occurs on the way from the evaporator to the vents.
If the required values of the front temperature sensors are not reached, perform fault finding in the case of a temperature increase after the evaporator.
• If the measured value in one or two temperature sensors deviates from the measured values of the other temperature sensors, check this temperature sensor and the control motor which activates the temperature door upstream from this temperature sensor using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- End "Guided Fault Finding" of the A/C system on the Climatronic control module and on the rear A/C display control head (E265) , and select the "Read measured values" function using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- Compare the previously determined measured value of the Evaporator vent temperature sensor to the measured values of the Left rear upper body vent temperature sensor (G635) , Right rear upper body vent temperature sensor (G636) , Left rear footwell vent temperature sensor (G637) and Right rear footwell vent temperature sensor (G638).
• Target values: The displayed measured values of the Left rear upper body vent temperature sensor, Right rear upper body vent temperature sensor, Left rear footwell vent temperature sensor and Right rear footwell vent temperature sensor may be a maximum of 9° C greater than the displayed measured value of the evaporator vent temperature sensor.
If the required values are not reached, determine the cause of the malfunction. Refer to => [ Malfunction Determination - Cooling Output of Front A/C System OK but Required Values Not Achieved In Rear - Comfort System ] Malfunction Determination - Cooling Output of Front A/C System OK But Required Values Not Achieved In Rear - Comfort System.
Set the following on the control head, the Climatronic control module (J255) :
- Use the knobs - 1, 5 - on the control head, the Climatronic control module (J255) , to set the temperature setting for the driver side and the front passenger side to "warm".
• "HI" displayed in the display - 3 - of the Climatronic control module and the rear A/C display control head (E265).
- Press the SYNC button - 10 - on the Climatronic control module.
• The settings of the front driver side are applied to the front passenger side and also on the rear A/C display control head.
• The display for the preselected temperature changes for all vents from "LO" to "HI" - the driver and front passenger side, for the left and right rear.
• If the selected temperature for the driver side on the Climatronic control module is not applied for all vents, press the SYNC button on the Climatronic control module again.
- Select the "Read measured values" function of the A/C system on the Climatronic control module using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- Read off the displayed measured values of the various temperature sensors Left vent temperature sensor (G150) , Right vent temperature sensor (G151) , Left footwell vent temperature sensor (G261) and Right footwell vent temperature sensor (G262).
• Target values: The measured temperature for all temperature sensors increases to above 50°C (depending on the instantaneous engine temperature).
• In vehicles without a coolant recirculation pump (V50) , the engine speed must be increased minimally to approximately 1400 RPM as necessary to reach the necessary coolant flow through the heat exchanger of the heater in the air distributor housing.
• Decrease the speed of the fresh air blower (V2) for vehicles with the start-stop system if necessary. The delivery output for the coolant pump (V50) is not always sufficient enough to reach the required heating output, when the engine is idle and the maximum fresh air blowing speed is set.
• The coolant pump (V50) maintains the refrigerant flow through the heater core in the A/C system when the engine is not running for vehicles with a start-stop system.
The required values are achieved at all temperature sensors:
• Continuation of the test - in vehicles with a rear Climatronic A/C display control head (E265) , check the rear heating output.
If the required values are not reached on any of the temperature sensors (and also not at a higher speed, diminished speed for the fresh air blower (V2) ):
• Check the activation and function of the coolant recirculation pump (V50) and the coolant shut-off valve (N82) using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
• Check the incorporation of the A/C system into the coolant circuit. Refer to => [ Integration of A/C Unit in Coolant Circuit ] Integration of A/C Unit In Coolant Circuit.
• Check coolant circuit bleeding. Refer to => [ Bleeding the Coolant Circuit ] Bleeding the Coolant Circuit.
• Check the heating output of the A/C system at an engine speed of 1500 to 2000 RPM (repeat the test at a higher engine speed). If the required heating output is not reached at this engine speed, the malfunction is not in the A/C unit but rather in the coolant circuit (incorporation of the A/C system into the coolant circuit, engine coolant pump delivery, the coolant flowing through the heat exchanger in the front A/C unit, incorporation of the coolant recirculation pump/coolant shut-off valve or into the coolant circuit, etc.). Refer to => [ Integration of A/C Unit in Coolant Circuit ] Integration of A/C Unit In Coolant Circuit and => [ Bleeding the Coolant Circuit ] Bleeding the Coolant Circuit.
• Check the engine coolant thermostat (the engine coolant may not heat properly if the thermostat is malfunctioning).
• Check the engine coolant pump for proper functioning (in the case of a malfunctioning coolant pump or an incorrectly incorporated coolant recirculation pump, insufficient coolant may be flowing through the heater core for the heater in the air distributor housing).
If the required values are not reached at only one or two temperature sensors:
• Check coolant circuit bleeding. Refer to => [ Bleeding the Coolant Circuit ] Bleeding the Coolant Circuit.
• Check the activation and function of the various control motors for the temperature doors in the A/C unit using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
• Check the measured values of the various temperature sensors using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
• Perform fault finding in the case of a temperature increase after the evaporator if the determined temperatures are too high in the cold setting.
• Check the foam seal at the heater core for the air distributor housing heater if the determined temperatures are too low in the warm setting or the deviation on the left and right is too high. Refer to => [ Heater Core ] Service and Repair.
Additional test in vehicles with a rear Climatronic A/C display control head (E265), check the rear heating output.
The heating output and activation of the temperature doors of the front A/C system were tested and are OK. Refer to => [ Comfort Vehicles - Heating Output and Activation of Temperature Doors, Checking ].
- Set the air distribution on the rear A/C display control head via the button - 4 - so that the air comes out approximately evenly from the vents in the B-pillars and the rear center console - displayed in the display - 1 - of the rear A/C display control head.
- Read off the measured values of the various temperature sensors Left rear upper body vent temperature sensor (G635) , Right rear upper body vent temperature sensor (G636) , Left rear footwell vent temperature sensor (G637) and Right rear footwell vent temperature sensor (G638) displayed in the "Read measured values" function using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
• In addition, a commercially available thermometer can be used to measure the temperature of the air coming out of the vents in the rear center console (left and right).
• Target values: The measured temperature for all temperature sensors increases to above 50°C (depending on the instantaneous engine temperature).
• In vehicles without a coolant recirculation pump (V50) , the engine speed must be increased minimally to approximately 1400 RPM to reach the necessary coolant flow through the heat exchanger of the heater in the air distributor housing.
• Decrease the speed of the fresh air blower (V2) for vehicles with the start-stop system if necessary. The delivery output for the coolant pump (V50) is not always sufficient enough to reach the required heating output, when the engine is idle and the maximum fresh air blowing speed is set.
The required values are achieved at all temperature sensors:
• Continuation of the test - check the separation for the temperature control between the left and right side in the A/C unit.
If the required values cannot be reached at one or several of the temperature sensors (not even with an increased engine speed):
• Check the activation and function of the control motors in the rear vent air guide and in the A/C unit using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
• Check the measured values of the various temperature sensors in the rear air guides using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
• Since the air cooled by the A/C unit must flow backward through the air guide channel under the center console, it may take some time for the air at the rear vents to reach the required values.
• If the required temperature is not achieved at a temperature sensor, change the setting at the Rear A/C display control head (E265) so that more air flows past this temperature sensor.
Continuation of the A/C unit heating output test - check the separation for the temperature control between the left and right side in the A/C unit.
- Use the knobs on the Climatronic control module (J255) , and the rear A/C display control head (E265) to set the temperature setting for the passenger side (front and rear) to cold.
• "LO" displayed in the display of the Climatronic control module and the rear A/C display control head for the front passenger side.
- The temperature setting for the driver side (front and rear) remains set to warm.
• "HI" displayed in the display of the Climatronic control module and the rear A/C display control head for the driver side.
- End "Guided Fault Finding" of the rear A/C display control head and on the Climatronic control module (J255) select the "Read measured values" function using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
- Let the A/C system run for several minutes with this setting.
• The A/C compressor is switched on - the indicator lamp in the AC button comes on.
- Compare the measured value of the evaporator vent temperature sensor (G263) to the measured values of the Left vent temperature sensor (G150) , Right vent temperature sensor (G151) , Left footwell vent temperature sensor (G261) and Right footwell vent temperature sensor (G262).
• At the temperature setting "warm" for one side (the driver or front passenger side), the target outflow temperature at the evaporator is regulated to a higher value (up to approximately 10° C (50° F)) by the Climatronic control module (J255).
• The temperature of the air flowing out of the rear vents is also regulated with a rear A/C display control head (E265) by the Climatronic control module (J255).
• Target values: On the Left vent temperature sensor (G150) and Left footwell vent temperature sensor (G261) , the temperature remains above 45° C (113° F) (depending on the current engine temperature).
• On the Right vent temperature sensor (G151) and Right footwell vent temperature sensor (G262) , the temperature drops to a value which may be a maximum of 15° C (59° F) higher than the measured value of the evaporator vent temperature sensor (G263) within 5 minutes.
• A warmer temperature is set at the left rear center console vent than at the right vent.
• The temperatures of the temperature sensors on one side (Left vent temperature sensor and Left footwell vent temperature sensor as well as Right vent temperature sensor and Right footwell vent temperature sensor) displayed in the "Read measured values" function equalize within 5 minutes (the particular temperature difference is less than 9° C).
- Record the measured value of the evaporator vent temperature sensor (G263).
- Finish the "Guided Fault Finding" for the A/C system on the Climatronic control module (J255) and select the "read measured value" function on the rear A/C display control head (E265). Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding" Function.
- Compare the measured value of the evaporator vent temperature sensor to the measured values of the Left rear upper body vent temperature sensor (G635) , Right rear upper body vent temperature sensor (G636) , Left rear footwell vent temperature sensor (G637) and Right rear footwell vent temperature sensor (G638).
• Target values: On the Left rear upper body vent temperature sensor and Left rear footwell vent temperature sensor, the temperature remains above 45° C (113° F) (depending on the current engine temperature).
• On the Right rear upper body vent temperature sensor and Right rear footwell vent temperature sensor, the temperature drops to a value which may be a maximum of 15° C (59° F) higher than the measured value of the evaporator vent temperature sensor (G263) within 5 minutes.
• The temperatures of the temperature sensors on one side Left rear upper body vent temperature sensor/Left rear footwell vent temperature sensor as well as Right rear upper body vent temperature sensor/Right rear footwell vent temperature sensor displayed in the "Read measured values" function equalize within 5 minutes (the particular temperature difference is less than 9° C (48° F)).
If the target values are reached, the test is complete.
• If the temperature for the driver side is set to "cold" and the temperature for the front passenger side is set to "warm", this test can be performed again using opposite measured values.
If the specified values are not reached, check the following:
• Check the activation and function of the various control motors for the temperature doors in the A/C unit (depending on where the target values were not reached) using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
• Check the activation and function of the two control motors in the rear air guide channel and the measured values of the various temperature sensors in the rear air guides using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
• Check the foam seal on the heat exchanger for the heater of the A/C unit (depending on where the target values were not reached). Refer to => [ Heater Core ] Service and Repair.
• Check coolant circuit bleeding. Refer to => [ Bleeding the Coolant Circuit ] Bleeding the Coolant Circuit.
• If present, check the activation and function of the coolant recirculation pump (V50) and the coolant shut-off valve (N82) using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
• Check the engine coolant pump for proper functioning (in the case of a malfunctioning coolant pump or an incorrectly incorporated coolant recirculation pump, insufficient coolant may be flowing through the heat exchanger for the heater in the front and rear A/C unit).
• Check the incorporation of the A/C system into the coolant circuit. Refer to => [ Integration of A/C Unit in Coolant Circuit ] Integration of A/C Unit In Coolant Circuit.
Fault finding in the case of a temperature increase downstream from the evaporator - in the A/C unit
• The test of the heating output and the activation of the temperature doors was performed.
- Clamp off both coolant hoses to the heat exchanger of the front A/C unit, for example, with hose clamps up to 40 mm (3093). Refer to => [ Integration of A/C Unit in Coolant Circuit ] Integration of A/C Unit In Coolant Circuit.
- Repeat the test of the heating output and activation of the temperature doors with the setting of "LO" on the front and rear control head. Refer to => [ Comfort Vehicles - Heating Output and Activation of Temperature Doors, Checking ].
- Compare the measured value of the evaporator vent temperature sensor (G263) to the measured values of the Left vent temperature sensor (G150) , Right vent temperature sensor (G151) , Left footwell vent temperature sensor (G261) and Right footwell vent temperature sensor (G262) (pay attention to the permissible deviation). Refer to => [ Comfort Vehicles - Heating Output and Activation of Temperature Doors, Checking ].
- Compare the measured values of the Left rear upper body vent temperature sensor (G635) , Right rear upper body vent temperature sensor (G636) , Left rear footwell vent temperature sensor (G637) and Right rear footwell vent temperature sensor (G638) to the previously measured value of the evaporator vent temperature sensor (G263) (pay attention to the permissible deviation). Refer to => [ Comfort Vehicles - Heating Output and Activation of Temperature Doors, Checking ].
