Heating Performance, Checking
Heating Performance, Checking
• If coolant circuit is not completely bled after filling, air may accumulate in heater core of heater, thus reducing heating performance, additional noises may occur or customer may complain of different air temperatures flowing out of vents at driver side and front passenger side.
Corrective action for poor heating output or noises from coolant circuit
- Perform a lengthy test drive at high engine speed (at least 10 minutes, engine speed above 2500 rpm). Select a low gear during the test to prevent excessive vehicle speed.
- If customer complains of poor heating performance at specific engine speeds, check incorporation of heater core of heater in the coolant circuit. If both coolant hoses (supply and return) of engine are interchanged, coolant is flowing in the wrong direction through the heater core.
- In vehicles with a parking/auxiliary heater, make sure the Recirculation pump (V55) on the parking heater is working correctly and that the parking heater is incorporated side the coolant circuit.
Requirements for reaching maximum heating performance
• Coolant circuit has been bled according to specifications.
• All air ducts, covers and seals OK and properly installed.
• Air flow through dust and pollen filter is not obstructed by dirt. Refer to => [ Dust and Pollen Filter ] Service and Repair.
• Engine is warm.
• The Bowden cable and the release cable on the temperature doors are OK.
• Engine coolant thermostat is OK.
• The foam seal on the heat exchanger is OK. Refer to => [ Heater Core ] Heater Core.
• On diesel vehicles, the auxiliary heater and the Heater control module (J65) are OK. Refer to => [ Heater Controls ] Heater Controls, and Vehicle diagnosis, testing and information system (VAS5051B) under "Guided Fault Finding" (perform Guided Fault Finding on the auxiliary air heater).
• In vehicles with a gasoline direct fuel injection engine FSI, activation of Engine Control Module (ECM) by Heater control module (J65) OK. Refer to=> [ Heater Controls ] Heater Controls.
Test Prerequisites
• Coolant circuit has been bled according to specifications.
• All air guides, covers and seal OK and properly installed.
• Air flow through dust and pollen filter not obstructed by dirt.
• Engine is warm.
• Vehicle not exposed to sunlight.
Heating Performance, checking
- Close hood.
- Close doors, windows and sun roof.
- Open all dash panel vents.
- Measure the ambient temperature (temperature in workshop).
- Start the engine.
- Turn the temperature switch 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.
• The heater works in fresh air mode, the indicator light for the recirculation button - D - does not light up.
• Fresh Air Blower runs at maximum speed.
Target values:
• The temperature of the air coming out of the left and right vents in the instrument panel is maximum 15 °C greater than in the previously measured ambient temperature.
• The temperature difference between the air coming out of the left and right instrument panel vents is less than 8 °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
• The temperature of the air coming out of the left and right instrument panel vents increases to a value greater than 55 °C (at an engine temperature of approximately 90 °C, depending on the current engine compartment temperature).
• The temperature difference between the air coming out of the left and right instrument panel vents 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
• The temperature drops within 5 minutes to a value, which is maximum 15 °C greater than the previously measured ambient temperature
If the specified values are not reached, check the following:
• If the required heat output is not reached
- Ventilation of coolant circuit.
- Incorporation of heater core for heater into coolant circuit.
- Bowden cable for setting the temperature and operating the temperature doors. Refer to=> [ Temperature Adjustment Cable ] Service and Repair.
- The foam seal on the heater core. Refer to=> [ Heater Core ] Heater Core.
- Function of temperature doors in air distribution housing. Refer to=> [ Air Routing and Distribution in Passenger Compartment ] Air Routing and Distribution In Passenger Compartment.
- Coolant regulator (engine coolant may not warm properly if regulator is malfunctioning).
• If the air coming out of the vents is too warm when it is set to "Cold"
- Bowden cable for setting the temperature and operating the temperature doors. Refer to=> [ Temperature Adjustment Cable ] Service and Repair.
- Function of temperature doors in air distribution housing. Refer to=> [ Air Routing and Distribution in Passenger Compartment ] Air Routing and Distribution In Passenger Compartment.
- The plenum chamber and seal between engine compartment and plenum chamber.