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A2

Removing and installing heater controls
Removing and installing heater controls
  Note
t  The heated rear window is switched via a relay actuated by the control unit in the heater controls; check the function of the heated rear window switch -E15- → Chapter and → Current flow diagrams, Electrical fault finding and Fitting locations.
   
t  The warning lamp in button -A- lights up when heated rear window is switched on.
t  The warning lamp in button -B- lights up when recirculated-air mode is selected (check the function of the fresh-air and recirculated-air flap switch -E159- → Chapter).
t  Button -C- is exclusive to vehicles with diesel engine (apart from vehicles with a 1.2 l TDI engine with emissions standard “D 4”, 3 l Öko for Germany → Chapter). Not all vehicles with diesel engine built since 2003 feature the button -C-; it depends on the vehicle's equipment. This can be used to switch off the “additional heater” function (“Econ” operation). Check the function of the Econ button → Chapter) and the → Owner’s Manual → Current flow diagrams, Electrical fault finding and Fitting locations
t  In vehicles with a 1.6 l petrol direct injection engine (FSI), there is an additional switch installed in the heater control electronics. This switch is operated via the temperature preselection rotary knob and using this, the position of the temperature rotary knob is communicated to the engine control unit.
  A80-0157
t  A voltage of approx. 1.0 V is output via contact “13” of the heating controls and the connector -A- if the temperature rotary knob is within a range from the “cold” limit switch up to a maximum of approx. “11 o'clock” (1/3 of the way towards warm). If the temperature rotary knob is turned past “11 o'clock” towards “warm”, the voltage switches to approx. 3.5 V.
t  A voltage of approx. 5 V is applied at the 16-pin connector -B- between contacts “14” and “12” when the ignition is switched on. → Current flow diagrams, Electrical fault finding and Fitting locations
t  If, in the engine control unit, there is a voltage of approx. 3.5 V at the input for the signal from the heater controls when the coolant temperature is low, the mixture formation is changed in order to achieve better heating output and, when the engine is warm, the engine cooling map is influenced, and the coolant temperature is thereby limited to approx. 95 °C). For further information → Relevant Workshop Manual, Injection and Ignition system
t  Individual components of the heater controls (heated rear window control unit, the button for switching between recirculated air and fresh air and the lamps (LEDs) for illuminating the buttons and rotary knobs) cannot be replaced separately.
t  When the ignition is switched off and on again, the heated rear window remains off and the heater switches to or remains in fresh-air mode.
  A80-0227
t  To clear misted windows as quickly as possible, recirculated-air mode cannot be implemented with “air to windscreen”. The control unit switches off the recirculated-air mode approx. 15° before the rotary knob for air distribution -D- reaches the (air to windscreen) position, and the "ON" warning lamp in button -B- goes out. The heater remains in fresh-air mode when the rotary knob is turned back again.
t  The rotary switches and switches on the heater control are illuminated via terminals “58s” and “58d”. → Current flow diagrams, Electrical fault finding and Fitting locations
  A80-0157

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