A/C Compressor Regulator Valve (N280), Checking Switch-On Signal
A/C Compressor Regulator Valve (N280), Checking Switch-On Signal
Special tools, testers and auxiliary items required
• Adapter cable from the Connector Test Kit (V.A.G 1594 C)
• DSO Measuring Lead 1 & 2 (VAS 5051/8)
• 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 the procedure for checking a vehicle with an 8 cylinder TDI engine. The procedure can differ in vehicles with a 6 cylinder, 8 cylinder gasoline or 12 cylinder engine.
Preparation
- Switch off ignition.
- Remove the front noise insulation. Refer to Underbody Trim Panels.
Test Sequence
- Connect electrical harness connector - 2 - to the A/C compressor regulator valve.
- 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 activated by the vehicle electrical system control module (J519) upon request from the Climatronic control module (J255). Check using the Vehicle diagnostic tester in the "Guided Fault Finding" function and
• The above figure shows an A/C compressor where connector - A - to the vehicle wiring harness is connected directly to 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 activation of the A/C compressor regulator valve is displayed in the read measured values function of the Guided Fault Finding of the vehicle electrical system control module and the Climatronic control module. The maximum control current depends on the version of the Climatronic control module. Check using the Vehicle diagnostic tester in the "Guided Fault Finding" function and.
• The measured current flowing through the A/C compressor regulator valve is displayed in the read measured values function of the Guided Fault Finding of the Climatronic control module and in the read measured values function of the Guided Fault Finding of the vehicle electrical system control module. Check using the Vehicle diagnostic tester in the "Guided Fault Finding" function.
• If the required actual current is not flowing through the A/C compressor regulator valve, check the positive and ground connections of the vehicle electrical system control module 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, for example 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 a diameter of 0.5 mm 2.
- 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 -
- Set the operating mode test instruments: DSO (digital storage oscilloscope) on the vehicle diagnosis system (for example the Vehicle diagnostic tester ) using in the "Guided Fault Finding" function.
- Select the setting 5V/div = 0.5ms/div (5V DC and 0.5 milliseconds per unit).
- Start the engine.
- Adjust the temperature preset to maximum cooling on the Climatronic control module.
- Switch activation of the A/C compressor regulator valve on and off on the Climatronic control module by pressing the AC button (with indicator lamp when A/C compressor is on).
The following is displayed on the oscilloscope screen depending on the Climatronic control module setting:
- In operating mode OFF or AC off (indicator lamp in the AC button does not illuminate), no square wave signal (the A/C compressor regulator valve is not activated).
- In operating mode Auto and AC on (indicator lamps in buttons illuminate) and temperature preselection for maximum cooling, 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 desired cooling output, vehicle voltage, etc. (over the width of region - A -, the voltage is regulated via the A/C compressor regulator valve by the vehicle electrical system control module on the basis of 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 (duty cycle between 100% and greater than 30%, the A/C compressor regulator valve is activated so that the required compressor output is obtained to reach the specified temperatures) depending on the setting on the Climatronic control module and the measured environmental conditions.
• 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 compressor output) when Auto and AC ON are set (the indicator lamps in the buttons are on) and the temperature preset is set to LO.
• 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.
• Check the activation of the A/C compressor regulator valve, refer to => [ A/C Compressor Regulator Valve (N280), Checking Activation ] A/C Compressor Regulator Valve (N280), Checking Activation.