Basic Vehicles - Heating Output and Activation of Temperature Doors, Checking
Basic 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.
- Start the engine.
• The rear temperature selection potentiometer (G538) is installed in the rear center console only in a certain country version.
• The activation of the temperature doors for the rear vents (by the rear temperature door motor (V137) ) is performed by a characteristic curve in the Climatronic control module (J255). If the setting between the left and right side in the Climatronic Control Module and / or the setting on the Rear Temperature Selection Potentiometer (G538) differs very much, then the temperature doors for the rear vents are no longer set in the end stops. The actuation of the temperature flaps for the temperature of the air coming out of the rear vents depends on the setting of the on the rear temperature selection potentiometer which has a tendency to be somewhat warmer or cooler the air for the front vents.
Set the following 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".
• Use the button - 7 - to set the air flow direction to "footwell" and "instrument panel vent".
• If present, the rear temperature selection potentiometer (G538) - 1 - is set to "cold".
• The indicator lamp in the AUTO button goes out when the vent direction for the air and/or fresh air blower speed is manually changed.
• The maximum possible fresh air blower speed depends on several environmental conditions (on-board voltage, etc.).
• The instrument panel 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: 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 measured temperature of the air from the rear center console vents may 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.
- If the required values for the air out of the rear center console vents are not reached, perform malfunction determination. Refer to => [ Malfunction Determination - Cooling Output of Front A/C System OK but Required Values Not Achieved In Rear - Basic System ] Malfunction Determination - Cooling Output of Front A/C System OK But Required Values Not Achieved In Rear - Basic System.
Set the following on the Climatronic control module (J255) :
• "Warm" temperature preselection - both knobs - 2, 5 - are set to "warm".
• If present, the rear temperature selection potentiometer (G538) - 1 - is set to "warm".
- 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) / recirculation pump (V55) , 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.
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 reach at any of the temperature sensors (not even with an increased engine speed):
• 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 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 A/C unit, incorporation of the coolant recirculation pump/coolant shut-off valve into the coolant circuit, etc.). Refer to => [ Integration of A/C Unit in Coolant Circuit ] Integration of A/C Unit In Coolant Circuit.
• Check the engine coolant temperature regulator (the engine coolant may not heat properly if the regulator 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 heat exchanger 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 heat exchanger 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.
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 knob - 5 - on the Climatronic control module (J255) , to set the temperature setting for the passenger side (front and rear) to "cold".
- The temperature setting for the driver side (front and rear) remains set to "warm".
- 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 this setting.
• The A/C compressor is switched on, the indicator lamp in the AC button - 6 - 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.
• The temperature of the air flowing out of the rear vents is regulated by the Climatronic control module.
• Target values: On the Left vent temperature sensor and Left footwell vent temperature sensor, the temperature remains above 45° C (113° F) (depending on the current engine temperature).
• On the Right vent temperature sensor and Right 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.
• In the case of a setting on the control head of "warm" for one side and "cold" for the other side, the air for the vent in the rear center console is no longer regulated. It is heated to the maximum.
• 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 (48° F)).
If the target values are reached, the test ends in vehicles without a rear temperature selection potentiometer (G538).
Vehicles with a Rear temperature selection potentiometer (G538) ,
- Set the temperature for the right side on the Climatronic control module (J255) to "warm" and wait several minutes.
- Measure the temperature of the air from the rear center console vent.
- On the Rear temperature selection potentiometer (G538) , set the thumbwheel - 1 - to "cold".
• Measure the temperature of the air from the rear center console vents.
- On the Rear temperature selection potentiometer, set the thumbwheel to "warm".
• The temperature of the air from the rear center console vents increases.
• The temperature of the air from the rear center console vents is regulated depending on the setting of the Rear temperature selection potentiometer and the Climatronic control module only as a cooler or warmer tendency compared to the instrument panel vents.
- Check the function of the Rear temperature selection potentiometer using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the Climatronic control module.
If the target values are reached, the test is complete.
Continued for all
• 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 target 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 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 "cold" on the control head. Refer to => [ Basic 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).
