SEAT Workshop Service and Repair Manuals

Check the activation signal for the Compressor regulation valve, air conditioning -N280- –  Switch ignition OFF. –  Remove the upper engine protection element (for example, for the 4-cylinder engine the connector is reached from above) → Engine, mechanics; Rep. Gr.13. –  Remove the sound proofing → Bodywork, exterior fitting work; Rep. Gr.50.

–  Disconnect the connection to the Compressor regulation valve, air conditioning -N280- on pin -1-.

–  Reestablish the connection using the adapter cable from the auxiliary measurement set -VAG 1594C- between the connector -A- and the connector -B- on the regulation valve.   Note t  During the activation of the Compressor regulation valve, air conditioning -N280-, the current measured by the control and indication panel Climatronic control unit -J255-/Air conditioning control unit -J301- is displayed in the measurement values block → Vehicle diagnosis, testing and information system VAS 5051.

t  Use can also be made of an improvised adapter cable for this test. This requires, for example, one connector -A- and -B- each (part number 1J0 973,702 and 1J0 973,802 and the corresponding plug contacts), two commercially available sockets for banana plugs -C- and three cables with cross section 0.5 mm2.

–  Connect the measurement cables -VAS 5051/8-to the adapter cables. –  Test cable(signal) to contact -2-. –  Test cable (screened, earth) to contact -1-. –  Adjust the operating mode on the central diagnosis -VAS 5051-. DSO (digital storage oscilloscope). –  Adjustment 5V/Div = 0.5ms/Div (5 volts DC and 0.5 milliseconds per unit). –  Start engine. –  Adjust the temperature on the passenger and driver sides in the Climatronic control unit -J255-/Air conditioning control unit -J301-. Vehicles fitted with Climatronic: –  Activate and deactivate in the Climate control unit -J255- using the keys “Auto” and “Off/On” or “Econ”, the activation of the Compressor regulation valve, air conditioning -N280-. Vehicles fitted with Climatic: –  Activate and deactivate in the Air conditioning control unit -J301- using the keys “AC” and selecting the speed “1” for the Fresh air turbine -V2-, the activation of the Compressor regulation valve, air conditioning -N280-. The adjustment function of the Climatronic control unit -J255-/Air conditioning control unit -J301- is displayed on the oscilloscope screen: –  In operation mode “OFF” or “Econ” without any rectangular wave signal (the regulation valve is not activated). Vehicles fitted with Climatronic:

–  In the operation mode “Auto” with the temperature control at minimum, there is a rectangular wave signal with a pulse width -A- of between 75 % and 100% (the regulation valve is activated). Vehicles fitted with Climatic: –  With the button “AC” pressed, the speed “1” of the Fresh air turbine -V2- selected and with the temperature control at minimum, there is a rectangular wave signal with a pulse width -A- of between 75 % and 100% (the regulation valve is activated).   Note t  The figure shows a signal with a duty cycle of approx. 80%. t  The width of the impulses -A- depends on the refrigeration performance required by the onboard voltage etc. (within the margin -A- the current is regulated through the Compressor regulation valve, air conditioning -N280- by the Climatronic control unit -J255-/Air conditioning control unit -J301-). t  The length -B- of the signals is always 2 milliseconds (corresponding to a frequency of 500 Hertz).

t  The duty signal is the result of the relationship between the width of the pulse -A- and the length of the signal -B-. –  Depending on the adjustment in the Climatronic control unit -J255-/Air conditioning control unit -J301- and the magnitudes of the environment conditions measured, the amplitude of the rectangular wave signal (duty cycle between 100% and more than 30%, the regulation valve is activated in such a way that enough power is directed to the compressor to reach the specified temperatures).   Note t  When the temperature setting is the lowest, the Compressor regulation valve -N280- is activated so that the maximum current of about 0.65 A flows across the Compressor regulation valve, air conditioning -N280- (maximum compressor performance). t  In control mode; duration of activation depends on the required cooling output, the vehicle voltage etc. The activation will last, however, until at least a current flow of 0.3 A is reached.