If The Specified Values Are Not Reached, Check The Following:
- Repeat the heating output at an engine RPM of approximately 1, 500 to 2, 000 (at a low fresh air blower speed on high voltage vehicles). If the heating output is not reached at the engine RPM (fresh air blower speed), the fault is not with the A/C unit but rather inside the coolant circuit (incorporation of the A/C system in the coolant circuit, engine coolant pump delivery, the coolant flowing through the heater core in the A/C unit, etc. Refer To HEATER CORE, REMOVING AND INSTALLING and COOLING SYSTEM/COOLANT [CAUA] , COOLING SYSTEM/COOLANT [CFSA] , COOLANT SYSTEM/COOLANT [CAED, CAEB, CPMB, CPMA] , COOLANT SYSTEM/COOLANT [CALA] , COOLANT SYSTEM/COOLANT [CAED, CAEB, CPMB, CPMA] - (2 Of 2)
- The activation and function of the Right Temperature Door Motor -V159-, the Left Temperature Door Motor -V159- and the activation of the left and right front temperature doors. Refer To, RIGHT TEMPERATURE DOOR MOTOR -V159-, REMOVING AND INSTALLING and use the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
- The activation and function of the Rear Temperature Door Motor -V137- and the activation of the left and right rear temperature doors (via the connecting rod). Refer To, TEMPERATURE REGULATOR DOOR MOTOR -V68- /REAR TEMPERATURE DOOR MOTOR -V137-, REMOVING AND INSTALLING and use the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
- Foam seal on heater core for the heater of A/C unit. Refer To HEATER CORE, REMOVING AND INSTALLING .
- The foam seal on the Auxiliary Air Heater Heating Element -Z35- on the honey comb. Refer To AUXILIARY HEATER HEATING ELEMENT -Z35-, REMOVING AND INSTALLING .
- The coolant circuit bleeding. Refer To COOLANT, DRAINING AND FILLING [CAUA] , COOLANT, DRAINING AND FILLING [CFSA] , COOLANT, DRAINING AND FILLING [CAEB, CPMA, CAED, CPMB] , COOLANT, DRAINING AND FILLING [CALA] and COOLANT, DRAINING AND FILLING [CAED, CAEB, CPMB, CPMA] .
- The incorporation of the heater core for the heater in the A/C unit into the coolant circuit. Refer To CONNECTION DIAGRAM - COOLANT HOSES [CAUA] , CONNECTION DIAGRAM - COOLANT HOSES [CFSA] , CONNECTION DIAGRAM - COOLANT HOSES [CAED, CAEB, CPMB, CPMA] and CONNECTION DIAGRAM - COOLANT HOSES [CALA] .
- The separations in the air distribution housing between the left and right side and between rear and front. Refer To OVERVIEW - AIR DISTRIBUTION HOUSING DOORS AND PARTITIONS .
- Coolant regulator (engine coolant may not warm properly if regulator is malfunctioning). Refer To COOLANT PUMP/THERMOSTAT [CAUA] , COOLANT PUMP/THERMOSTAT [CFSA] , COOLANT PUMP/COOLANT THERMOSTAT [CAED, CAEB, CPMB, CPMA] , COOLANT PUMP/THERMOSTAT [CALA] and COOLANT SYSTEM/COOLANT [CAED, CAEB, CPMB, CPMA]] (2 Of 2) .
- Check the engine coolant pump for proper function (if the coolant pump is defective, it is possible that not enough coolant is flowing through the heater core for the heater in the A/C unit). Refer To COOLANT PUMP/THERMOSTAT [CAUA] , COOLANT PUMP/THERMOSTAT [CFSA] , COOLANT PUMP/COOLANT THERMOSTAT [CAED, CAEB, CPMB, CPMA] , COOLANT PUMP/THERMOSTAT [CALA] and COOLANT SYSTEM/COOLANT [CAED, CAEB, CPMB, CPMA]] (2 Of 2) .
- For vehicles with a regulated coolant circuit (only installed on certain engines from MY 2011), the activation and function of these components (for example, the regulated coolant pump and the Cylinder Head Coolant Valve -N489-). Refer To COOLANT PUMP/THERMOSTAT [CAUA] , COOLANT PUMP/THERMOSTAT [CFSA] , COOLANT PUMP/COOLANT THERMOSTAT [CAED, CAEB, CPMB, CPMA] , COOLANT PUMP/THERMOSTAT [CALA] and COOLANT SYSTEM/COOLANT [CAED, CAEB, CPMB, CPMA]] (2 Of 2) .
- The Coolant Recirculation Pump -V50- activation and function (if the coolant pump is faulty, it is possible that not enough coolant is flowing through the heater core for the heater in the A/C unit) using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
The Coolant Recirculation Pump -V50- is not installed on all vehicles (depending on the version, engine and when the vehicle was manufactured). The Recirculation Pump -V55- works as the Coolant Recirculation Pump -V50- on vehicles with optional equipment. The Auxiliary Heater Control Module -J364- activates the Recirculation Pump -V55- upon request of the Climatronic Control Module -J255- A/C display and control head when the engine RPM is low to support the engine coolant pump, depending on the vehicle version and the adaptation of the Auxiliary Heater Control Module -J364-, using the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
The Coolant Pump -V50- maintains the coolant flow through the heater core for the heater in the A/C unit when the engine is not running on vehicles with a Start/Stop System and on high voltage vehicles.
-- Using the knob on the Climatronic Control Module -J255- A/C display and control head, select the "warm" temperature setting on the driver side ("HI" for the driver and front passenger side in the Climatronic Control Module -J255- and MMI display).
-- Read the measured values of the temperature sensor after heat exchanger (Left Front Upper Body Vent Temperature Sensor -G385-, Right Front Upper Body Vent Temperature Sensor -G386-, Left Footwell Vent Temperature Sensor -G261- and Right Footwell Vent Temperature Sensor -G262-).
-- Using a commercially available thermometer, measure the temperature of the air coming out of the vents in the rear center console (left and right).
SPECIFIED VALUES:
- The temperature at the Left Front Upper Body Vent Temperature Sensor -G385- and Left Footwell Vent Temperature Sensor -G261- increases to above 52 °C (126 °F) within five minutes (depending on the engine temperature at the time).
- The temperatures of the temperature sensors displayed in the measure values block (Left Front Upper Body Vent Temperature Sensor -G385-, Right Front Upper Body Vent Temperature Sensor -G386-, Left Footwell Vent Temperature Sensor -G261- and Right Footwell Vent Temperature Sensor -G262-) even out within five minutes (the difference in temperature is less than 5 °C (41 °F) and the temperature is greater than 52 °C (126 °F)).
- The measured temperature coming out of the vents in the left and right side of the rear center console increases but does not reach the displayed temperatures for the temperature sensors (Left Front Upper Body Vent Temperature Sensor -G385-, Right Front Upper Body Vent Temperature Sensor -G386-, Left Footwell Vent Temperature Sensor -G261- and Right Footwell Vent Temperature Sensor -G262-) (temperature has a tendency to be cooler than the setting on the Rear Temperature Selection Potentiometer -G538-). Refer To THE ACTIVATION OF THE TEMPERATURE DOORS FOR THE REAR VENTS (BY THE REAR TEMPERATURE DOOR MOTOR -V137-) IS PERFORMED BY A CHARACTERISTIC CURVE STORED IN THE CLIMATRONIC CONTROL MODULE -J255- A/C DISPLAY AND CONTROL HEAD. .
Depending on the engine, for example, on the 8-Cylinder engine, it may be necessary to increase the engine RPM from 1, 200 to 1, 500 to reach the required temperature. The heating output of the engine or coolant flowing through the heater core may not be sufficient when the engine is running in idle to bring the necessary warming energy into the heater core (for example, on an 8-Cylinder engine with an idle RPM of approximately 650).
At the "warm" temperature setting for the driver and front passenger side, the specified outflow temperature on the evaporator is regulated to approximately 10 °C (50 °F) by the Climatronic Control Module -J255- A/C display and control head.
On high voltage vehicles, reduce the Fresh Air Blower -V2- speed if necessary. The Coolant Recirculation Pump -V50- delivery is not always enough to supply the requested heat output when the engine is not running and the fresh air blower is set to the highest setting.
If the specified values are not reached, check the following. Refer To IF THE SPECIFIED VALUES ARE NOT REACHED, CHECK THE FOLLOWING: .
If The Specified Values Are Not Reached, Proceed As Follows:
-- Set the Rear Temperature Selection Potentiometer -G538- to "warm" (installed in the rear center console vent).
-- Using a commercially available thermometer, measure the temperature of the air coming out of the vents in the rear center console and the rear footwells (left and right sides) and compare with the displayed measured values for the temperature sensors (Left Front Upper Body Vent Temperature Sensor -G385-, Right Front Upper Body Vent Temperature Sensor -G386-, Left Footwell Vent Temperature Sensor -G261- and Right Footwell Vent Temperature Sensor -G262-).
SPECIFIED VALUES:
- The measured air temperature coming out of the vents in the rear center console and the rear footwell vents (left and right side increases and reaches within 5 minutes a value, which is 10 °C (50 °F) less than the small value measured and displayed by the temperature sensors.
- The deviation between the measured temperature on the left and right side is less than 5 °C (41 °F).
If The Specified Values Are Not Reached, Check The Following:
- Check the activation and function of the Rear Temperature Door Motor -V137- and the activation of the left and right rear temperature doors (via the connecting rod). Refer To, TEMPERATURE REGULATOR DOOR MOTOR -V68- /REAR TEMPERATURE DOOR MOTOR -V137-, REMOVING AND INSTALLING and use the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
- Additional tests should the specified values not be reached. Refer To IF THE SPECIFIED VALUES ARE NOT REACHED, CHECK THE FOLLOWING: .
If The Specified Values Are Not Reached, Proceed As Follows:
-- Using the knob on the Climatronic Control Module -J255- A/C display and control head, select the "cold" temperature setting for the front passenger side ("LO" in the Climatronic Control Module -J255- and MMI display).
-- Compare the measured value of the Evaporator Vent Temperature Sensor -G263- with the measured values for the Right Front Upper Body Vent Temperature Sensor -G386- and the Right Footwell Vent Temperature Sensor -G262- and read the measured values for the Left Front Upper Body Vent Temperature Sensor -G385- and the Left Footwell Vent Temperature Sensor -G261-.
SPECIFIED VALUES:
- The measured and displayed temperatures at the Left Front Upper Body Vent Temperature Sensor -G385- and Left Footwell Vent Temperature Sensor -G261- change slightly and remain greater than 52 °C (126 °F) (depending on the engine temperature at the time).
- The temperature at the Right Front Upper Body Vent Temperature Sensor -G386- and Right Footwell Vent Temperature Sensor -G262- drops and after five minutes at the latest, it reaches a value of maximum 10 °C (50 °F) greater than the values of the Evaporator Vent Temperature Sensor -G263-.
Depending On The Engine, For Example, On The 8-Cylinder Engine, It May Be Necessary To Increase The Engine RPM From 1, 200 To 1, 500 To Reach The Required Temperature. The heating output of the engine or coolant flowing through the heater core may not be sufficient when the engine is running in idle to bring the necessary warming energy into the heater core (for example, on an 8-Cylinder engine with an idle RPM of approximately 650).
At the "warm" temperature setting for the driver and front passenger side, the specified outflow temperature on the evaporator is regulated to approximately 10 °C (50 °F) by the Climatronic Control Module -J255- A/C display and control head. If the "cold" temperature setting is selected for one side, the Climatronic Control Module -J255- A/C display and control head lowers the specified outflow temperature on the evaporator and regulates this to approximately 2 °C (36 °F).
On high voltage vehicles, reduce the Fresh Air Blower -V2- speed if necessary. The Coolant Recirculation Pump -V50- delivery is not always enough to supply the requested heat output when the engine is not running and the fresh air blower is set to the highest setting.
If the specified values are not reached, check the following. Refer To IF THE SPECIFIED VALUES ARE NOT REACHED, CHECK THE FOLLOWING: .
If the specified values are reached, the test is complete.