Heating Performance - With Automatically Regulated A/C System, Checking

Test Requirements 

• Coolant circuit has been bled according to specifications, refer to COOLING SYSTEM, DRAINING AND FILLING .
• All air guides, covers and seal OK and properly installed.
• Air flow through dust and pollen filter not obstructed by dirt.
• Engine is warm
• The Climatronic control module was checked and erased and the basic setting was performed using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.
• The Climatronic control module coding has been checked using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.
• The Climatronic control module adaptation has been checked using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.
• Vehicle not exposed to sunlight

Heating Performance, Checking 

-- Close hood.

-- Close doors, windows and sun roof.

-- Initiate a Guided Fault Finding on the A/C system using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

-- Open all dash panel vents.

-- Read the measured values for the Left Vent Temperature Sensor -G150- and Right Vent Temperature Sensor -G151- using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

-- Check and compare the displayed measured values.

• Specified temperature: maximum 12 °C, depending on the outside temperature, variance between the measured values: less than 3 °C.

-- Set air distribution to instrument panel vents.

-- Set temperature preselect for left side (driver side) on Climatronic control module to Hi.

-- Read the left vent temperature sensor and right vent temperature sensor displayed measured values.

Specified Values 

• In the display field with the measured value for the left vent temperature sensor the temperature goes above 55 °C when the engine temperature is approximately 90 °C. In the display field with the measured value for the right vent temperature sensor the temperature goes up less than 10 °C.

-- Set temperature preselect for right side (front passenger side) on Climatronic control module to Hi.

-- Read the displayed measured values for the left vent temperature sensor and right vent temperature sensor.

Specified Values 

• In the display field with the measured value for the left vent temperature sensor, the temperature increases to approximately the engine temperature; the difference between the display fields for the measured fields of the left vent temperature sensor and the right vent temperature sensor is less than 8 °C.

-- Set temperature preselect for driver side on Climatronic control module to LO.

-- Read the displayed measured values for the left vent temperature sensor and right vent temperature sensor.

Specified Values 

• Temperature for left side (driver side) decreases within 5 minutes to less than 12 °C depending on ambient temperature.

-- If necessary, perform this test step for front passenger side in the same way.

If the specified values are not reached, check the following: 

-- Ventilation of coolant circuit, refer to DESCRIPTION AND OPERATION and refer to DIAGNOSIS AND TESTING .

-- Incorporation of heater core for heater in A/C unit into coolant circuit, refer to DISASSEMBLY AND ASSEMBLY and refer to HEATER UNIT .

-- Activation and function of Left Temperature Door Motor -V158- and of Right Temperature Door Motor -V159- using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

-- Foam seal on heater core for heater of A/C unit, refer to HEAT EXCHANGER .

-- Function of temperature doors in air distribution housing, refer to AIR ROUTING AND DISTRIBUTION IN PASSENGER COMPARTMENT .

-- Coolant regulator (engine coolant may not warm properly if regulator is malfunctioning), refer to THERMOSTAT, CHECKING .