Heating Performance - With Manually 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 A/C Control Module -J301- was checked and erased, and a basic setting was performed 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.

-- Start the engine and let it run for a few minutes with maximum cooling output. The A/C compressor is switched on, the indicator lamp in the AC  button comes on and the temperature rotary switch is turned all the way to cold.

-- Set the air flow direction to instrument panel vents via the air distribution rotary switch.

-- Set speed 4 on fresh air blower rotary switch.

-- Measure temperature of the air flowing out of left and right instrument panel vents using a thermometer.

-- Compare the measured values with the displayed measured value from the Evaporator Vent Temperature Sensor -G263-. The measured values may not be smaller and after 5 minutes be greater than maximum 3 °C, than the value of the evaporator vent temperature sensor.

Specified Values 

• Temperature maximum 12 °C, depending on ambient temperature, the difference between the measured values is less than 3 °C.

-- Set the highest possible temperature (temperature rotary switch turned all the way to warm).

-- Measure temperature of the air flowing out of left and right instrument panel vents using a thermometer.

Specified Values 

• Temperature increases to greater than 55 °C at an engine temperature of approximately 90 °C, deviation between the left and right side is less than 8 °C.

-- Set the lowest possible temperature (turn the temperature rotary switch all the way to cold).

-- Measure temperature of the air flowing out of left and right instrument panel vents using a thermometer.

Specified Values 

• Temperature decreases within 5 minutes to less than 12 °C depending on ambient temperature.

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.

-- Activation and function of Temperature Regulator Door Motor -V68-. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".

-- 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 GUIDE IN AIR DISTRIBUTION HOUSING .

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