A/C Compressor Regulator Valve (N280), Checking Switch-On Signal
A/C Compressor Regulator Valve (N280), Checking Switch-On Signal
• The test for an A/C compressor manufactured by "Denso" of type "6 SEU 14" is described in the following. Test is to be performed in the same way for vehicles with a different compressor type or a different manufacturer.
• Next, testing is described for vehicles equipped with a 2.0L TFSI and a 3.2L MPI engine. This procedure might be different for vehicles that have a different 4 or 6 cylinder engine, or a 5 cylinder engine.
Preparation
- Switch off ignition.
- Remove the engine cover (for example, on 4 cylinder vehicles, where the connector is accessible from the top; not necessary on a 2.0L TFSI vehicle).
- Remove the center noise insulation (for example, on 2.0L TFSI and 3.2L MPI vehicle, the connector is not accessible from the top).
Test Sequence
- Disconnect electrical connector - B - on A/C Compressor Regulator Valve (N280) - A -.
- Re-establish the connection between connector - A - and connector - B - on A/C compressor regulator valve using an adapter cable from Connector test kit (V.A.G 1594 C).
• The activation of the A/C compressor regulator valve and the current that flows through the A/C compressor regulator valve, and which the Climatronic control module (J255) measure, are displayed on the Climatronic control module measured values block. Check using Vehicle diagnosis, testing and information system (VAS5051B) under "Guided Fault Finding".
• An adapter cable can also be used for this test. To do this, e.g. use one connector each - A - and - B - (part number 1J0 973 702 and 1J0 973 802 and relevant terminal contacts), two standard sockets for banana connectors - C - and two wires with 0.5 mm 2 diameter.
- Connect DSO measuring leads 1 & 2 (VAS 5051/8) to the adapter leads.
- Measuring lead (signal wire) to terminal - 2 - of connector - B -
- Measuring lead (shielding, Ground) to terminal - 1 - of connector - B -
- Set operating mode Test Instruments DSO (Digital Storage Oscilloscope) on Vehicle diagnosis, testing and information system (VAS5051B).
- Then select the 5 V/Div = 0.5 ms/Div (5V DC and 0.5 milliseconds per unit) setting.
- Start the engine.
- Set temperature preselect on Climatronic control module (J255) to "Cold" setting (maximum cooling performance)
- On Climatronic control module, switch activation of A/C Compressor Regulator Valve (N280) on and off by pressing the "AC" button (with indicator light when compressor is on).
Shown on screen of oscilloscope, depending on setting of Climatronic control module:
- 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 is not activated).
- In operating mode "Auto" and "AC on" (indicator lights in buttons come on) and temperature preselect at "Cold" setting (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%.
• Impulse width - A - depends on the cooling performance desired, the electrical system voltage, etc. (over the width of region - A -; voltage is regulated via the A/C Compressor Regulator Valve by Climatronic control module).
• The signal distance - B - is always 2 milliseconds (corresponds to frequency of 500 Hertz).
• The duty cycle is determined by the ratio of impulse width - A - and signal distance - B -.
- The impulse width of the square wave signal changes (duty cycle between 100% and greater than 30%, regulator valve is activated so that required compressor output is obtained to reach the specified temperatures) depending on setting at Climatronic control module and measured surrounding conditions.
• Whenever the mode is adjusted to "Auto", and "AC On" (the indicator lamps on the buttons light up), and the temperature preset is set to stop "Cold", then the A/C compressor regulator valve is activated so that the maximum permissible current of approximately 0.65 A flows through the A/C compressor regulator valve (maximum A/C compressor output).
• In control mode, actuation time is governed by required cooling output and vehicle electrical system voltage, for example. It is however always of sufficient duration to achieve a mean current of 0.3 A.