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
• Connector Test Set (V.A.G 1594 C)
• Vehicle Diagnostic, Testing and Information System (VAS 5051 A) with DSO Measuring Leads 1 & 2 (VAS 5051/8)
• The test for an A/C compressor manufactured by Denso of type 7 SEU 16 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.
- Switch off ignition.
- Remove the engine cover (for example, connector is accessible from top in vehicles with 4 cylinder engine).
- Remove the noise insulation (for example, on vehicles equipped with a 4 cylinder, 2.0L TFSI engine or a 6 cylinder engine; on these engines, the connector is not accessible from the top).
- Disconnect electrical connection to A/C Compressor Regulator Valve (N280) at harness connector - 1 -.
- Reproduce the connection between connector - A - and connector - B - at regulator valve using an adapter cable from (V.A.G 1594 C).
• Vehicles with automatically regulated A/C system: Climatronic Control Module (J255) actuates the compressor via the A/C Compressor Regulator Valve (N280).
• The A/C control module (J301) controls the A/C compressor via the A/C compressor regulator valve on vehicles with a manual A/C system.
• The control of the A/C compressor regulator valve and the current measured by the Climatronic control module, or by the A/C control module that flows via the A/C compressor regulator valve is displayed in the measured values block for each A/C control module using Vehicle diagnosis, testing and information system (VAS5051B) in "Guided Fault Finding" function.
• An adapter cable can also be used for this test. To do this, e.g. use connectors - A - and - B - (part number 1J0 973 702 and 1J0 973 802 and relevant terminal contacts. Refer to Electronic Parts Catalog (ETKA)), two standard sockets for banana connectors - C - and two wires with 0.5 mm 2 diameter.
- Connect (VAS 5051/8) to the adapter leads.
- Measuring lead (signal wire) to terminal - 2 - on connector - A -.
- Measuring lead (shielding, ground) to terminal - 1 - of connector - A -.
- In Vehicle diagnosis, testing and information system (VAS 5051B) , select operating mode Test Instruments: DSO (Digital Storage Oscilloscope) and select setting 5V/Div = 0.5.5ms/Div (5V DC voltage and 5 milliseconds per unit)
- Start the engine.
- Vehicles with automatically regulated A/C system: set temperature preselect for driver and front passenger side to "Lo" on Climatronic Control Module (J255).
- Vehicles with a manual climate control system: turn temperature preselect rotary switch on A/C system controls ( A/C Control Module (J301) ) counter-clockwise to the "Cold" stop.
- Switch the A/C compressor regulator valve (N280) on and off using the Auto and Off/On buttons or the Econ or AC buttons on the Climatronic control module (vehicles with an automatic A/C system).
• Depending on the version of the A/C control head, it is possible to identify when "Econ"is on. Either the indicator lamp inside the ECON button will be on and the indicator lamp in the AC button will be off.
- Press the AC button (A/C control module) to activate the A/C compressor regulator valve (vehicles with a manually controlled A/C system).
Shown on screen of oscilloscope, depending on setting of Climatronic Control Module (J255) :
- No square wave signal (regulator valve is not activated) for operating mode "OFF" or "Econ" ("AC" off).
- A square wave signal with an impulse width - A - between 75% and 100% (regulator valve is activated) for operating mode "Auto" ("AC" on) and temperature setting "Lo" (temperature rotary switch at "cold" stop).
• The Fig. shows a signal with a duty cycle of approximately 80%.
• Impulse width - A - is dependent on desired cooling performance, vehicle voltage etc. (over the width of region - A -, voltage is regulated via A/C Compressor Regulator Valve (N280) by Climatronic Control Module (J255) / by A/C Control Module (J301) ).
• The signal distance - B - is always 2 milliseconds. This 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 (J255) / at A/C Control Module (J301) and measured surrounding conditions.
• With the "Auto" button pressed and the temperature set to "Lo" ("AC" on and the temperature rotary switch turned to "cold" manual climate control system), the A/C compressor regulator valve makes sure that the maximum permissible current of 065 A is flowing via the A/C compressor regulator valve (maximum A/C compressor performance).
• 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.