A5 Quattro Coupe V6-3.2L (CALA) (2009)
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Measuring lead (signal wire) to terminal - 2 - of connector - B -
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Measuring lead (shielding, Ground) to terminal - 1 - of connector - B -
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Set the measurement mode Diagnostic Operation System (VAS 5051/) : DSO (Digital Storage Oscilloscope)
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Select the settings 5V/div DC, 0.5ms/div (5V DC and 0.5 milliseconds per unit)
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Start the engine.
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Adjust the temperature preset to maximum cooling on the A/C Control Head Climatronic Control Module (J255).
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Switch the A/C Compressor Regulator Valve (N280) activation on and off by pressing the "AC" button (with an indicator light when the
compressor is on) on the A/C Control Head Climatronic Control Module (J255)
Shown on screen of oscilloscope, depending on setting of A/C control head Climatronic Control Module (J255):
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In operating mode "OFF" or "AC off" (indicator light in "AC" button does not come on), no square wave signal (the A/C Compressor Regulator
Valve (N280) is not activated).
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In operating mode "Auto" and "AC on" (indicator lights in buttons come on) and temperature preselect for maximum cooling output, a square
wave signal with an impulse width - A - between 75% and 100% (the control valve is activated).
‹› The Fig. shows a signal with a duty cycle of approximately 80%.
‹› The impulse width - A - is dependent upon the desired cooling performance, vehicle voltage, etc. (over the width of region - A - , the voltage is
regulated via the A/C Compressor Regulator Valve (N280) from the Vehicle Electrical System Control Module (J519) based on the request from
the A/C Control Head Climatronic Control Module (J255)).
‹› The signal distance - B - is always 2 milliseconds (corresponds to frequency of 500 Hertz).