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.
• The following describes checking a vehicle with a 6 cylinder TDI engine; the procedure can vary on vehicles with a different engine ( 4, 6 or 8 cylinder engine).
• Not installed on an electric A/C compressor; refer to => [ Electric A/C Compressor Removing from Bracket ] Electric A/C Compressor Removing From Bracket.
Preparation
- Turn off the ignition.
- Remove front noise insulation.
Test Sequence
- Disconnect electrical connector - B - on A/C compressor regulator valve - A -.
- Using an adapter cable from the connector test kit (V.A.G 1594 C) recreate the connection between terminal - A - and terminal - B - on the A/C compressor regulator valve.
• The A/C compressor regulator valve is controlled by the vehicle electrical system control module (J519) requested by the Climatronic control module (J255). Check via the the Vehicle diagnostic tester in "Guided Fault Finding" and.
• The above illustration shows a A/C compressor where the connector - A - leading to the vehicle wiring harness is directly connected on the A/C compressor regulator valve (connector - B -). Depending on the version of the A/C compressor, the connector - B - may also have a short wire.
• The A/C compressor regulator valve control is displayed in the vehicle electrical system control module (J519) measured values block. The maximum control current depends on the version of the Climatronic control module. Refer to the Vehicle diagnostic tester in "Guided Fault Finding".
• The measured current, that flows through the A/C compressor regulator valve, is displayed in the Climatronic control module measured values block and in the vehicle electrical system control module (J519) measured values block. Refer to the Vehicle diagnostic tester in "Guided Fault Finding".
• If the required actual current is not flowing through the A/C compressor regulator valve check Vehicle Electrical System Control Module (J519) positive and ground connections and the wire connections between the Vehicle Electrical System Control Module and the A/C Compressor Regulator Valve for short circuit, contact resistance and interchanged wires according to the wiring diagram.
• An adapter cable can also be used for this test. To do this, use one connector each - A - and - B - (part number 1J0 973 702 and 1J0 973 802 and related terminal contacts), two standard sockets for banana connectors - C - and two wires with 0.5 mm 2 diameter.
- Connect the DSO Measuring Lead 1 & 2 (VAS 5051/8) to the adapter cables.
- Measuring lead (signal wire) to terminal - 2 - of connector - B -
- Measuring lead (shielding, Ground) to terminal - 1 - of connector - B -
- In Vehicle Diagnostic Tester select operating mode Test Instruments: DSO (Digital Storage Oscilloscope)
- Select 5 V/Div = 0.5 ms/Div (5 volts DC and 0.5 milliseconds per unit)
- Start the engine.
- Adjust the temperature preset to maximum cooling on the Climatronic control module.
- Switch the A/C compressor regulator valve activation on and off by pressing the "AC" button (with an indicator lamp when the A/C compressor is on) on the Climatronic control module.
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 lamps 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 output, vehicle voltage, etc. (over the width of region - A -, the voltage is regulated via the A/C compressor regulator valve from the vehicle electrical system control module (J519) based on the request from the 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 depending on the Climatronic control module setting and the environmental conditions (duty cycle between 100% and larger than 30%, the A/C compressor regulator valve is activated so the compressor output necessary to reach the specified temperatures is achieved).
• 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 "Lo", 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.
• A/C compressor regulator valve, Checking, refer to => [ A/C Compressor Regulator Valve (N280), Checking Activation ] A/C Compressor Regulator Valve (N280), Checking Activation.