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Checking actuation of supplementary heater - TDI engine > < Heat output of heater

A1

Checking heating output
Checking heating output
Special tools and workshop equipment required
t  Commercially available thermometer (for measuring temperature; if applicable use thermometer with 2 probes for simultaneous measurement of temperature e.g. on right and left)
l  If the coolant circuit is not completely bled after filling, air may accumulate in the heating system heat exchanger and thus reduce the heat output. In addition, noise may occur or complaints may be received about differences in the temperature of the air from the vents.
Remedy if there is poor heating output or noise from the coolant circuit
–  Perform a test drive at fairly high engine speed (at least 10 minutes, engine speed above 2500 rpm). Select a low gear when doing so to prevent an excessively high vehicle speed.
–  In the event of complaints about poor heat output at certain engine speeds, check incorporation of the heating system heat exchanger into the engine coolant circuit → Rep. gr.19.
Test prerequisites for attaining maximum heat output
l  Check the coolant level → Rep. gr.19.
l  Coolant circuit bled in specified manner → Rep. gr.19.
l  All air ducts, covers and seals OK and properly installed
l  Air flow in dust and pollen filter not impaired by dirt; checking → Chapter
l  Engine at operating temperature
l  Flexible shaft and operating lever of temperature flap OK and properly fitted.
l  Engine thermostat OK → Rep. gr.19
l  Foam seal at heating system heat exchanger OK → Chapter.
l  On vehicles with TDI engine, operation of supplementary heater and actuation by heater control unit -J65- OK → Chapter. Check in „Guided fault-finding“ function, supplementary air heater → Vehicle diagnostic tester„Guided fault-finding“, TDI engine.
l  Actuation of engine control unit by heater control unit -J65- OK. Check in „Guided fault-finding“ function, TDI engine → Vehicle diagnostic tester.
   
Checking heat output
–  Close the front lid, doors, windows and sun roof.
–  Open the dash panel vents.
–  Measure the ambient temperature (temperature in workshop).
–  Start the engine.
–  Set the rotary temperature control -1- to the „Cold“ stop.
–  Set the rotary air distribution control -3- to „Dash panel vents“.
–  Set the rotary fresh air blower control -2- to speed „4“.
–  Use a thermometer to measure the temperature of the air emerging from the left and right dash panel vents.
  Note
t  The heater operates in fresh air mode, the indicator lamp in the air recirculation button -5- does not light.
t  The fresh air blower runs at maximum speed.
Specifications:
l  The temperature of the air emerging from the dash panel vents (left and right) should be max. 15° C higher than the ambient temperature (measured earlier).
l  The difference in the temperature of the air emerging from the left and right dash panel vents should be less than 8 °C.
–  Set the highest possible temperature (rotary temperature switch on „Warm“ stop).
–  Use a thermometer to measure the temperature of the air emerging from the left and right dash panel vents.
Specifications:
l  The temperature of the air emerging from the dash panel vents on the left and right increases to a value above 45 °C (at an engine temperature of approx. 90 °C).
l  The difference in the temperature of the air emerging from the left and right dash panel vents should be less than 8 °C.
  Note
At ambient temperatures below 10 °C, the temperature of the air emerging from the left and right dash panel vents will not always be higher than 45 °C in the selected setting „maximum fresh air blower speed, engine idling“. The engine speed is therefore to be increased to 1500 rpm when performing this test at low ambient temperatures.
–  Set the lowest possible temperature (rotary temperature switch on „Cold“ stop).
–  Use a thermometer to measure the temperature of the air emerging from the left and right dash panel vents.
Specifications:
l  Within 5 minutes, the temperature should drop to a value that is max. 15° C higher than the ambient temperature (measured earlier).
Check the following if readout does not match specifications:
If the air emerging from the vents is too warm in the „Cold“ setting:
–  Check the flexible temperature adjustment shaft and actuation of the temperature flaps → Chapter.
–  Check operation of the temperature flaps in the air distribution housing → Chapter „Removing and installing air distribution housing“.
–  Check the plenum chamber cover and the seal between the engine compartment and plenum chamber.
If the air emerging from the vents is too cold in the „Warm“ setting:
–  Check coolant circuit bleeding → Rep. gr.19.
–  Check incorporation of the heating system heat exchanger into the coolant circuit → Rep. gr.19.
–  Check the flexible temperature adjustment shaft and actuation of the temperature flap (the flap must reach both end stops) → Chapter.
–  Check the foam seal at the heating system heat exchanger → Chapter.
–  Check operation of the temperature flaps in the air distribution housing → Chapter „Removing and installing air distribution housing“.
–  Check the thermostat (the engine coolant may not become properly warm if the thermostat is defective) → Rep. gr.19.
–  Check operation of the temperature flaps in the air distribution housing → Chapter „Removing and installing air distribution housing“.
If no fault is found:
–  Increase the engine speed to approx. 1500 rpm and check the temperature again.
If the heat output is then OK:
–  Check the thermostat (the engine coolant may not become properly warm if the thermostat is defective) → Rep. gr.19.
–  Check the coolant pump → Rep. gr.19.
  A87-10864

Checking actuation of supplementary heater - TDI engine > < Heat output of heater