Checking cut-in signal for compressor regulating valve N280 — AUDI

🧭 Before you start

Fits: Audi A6 C6 (4F, 2004–2011)

• Special tools named: VAS 5051

📋 Procedure

1. Switch off ignition.
2. Remove noise insulation General body repairs, exterior50.
3. Mark connector (A). [Note: On vehicles with 8-cyl. engine, this connector is not attached to the compressor but rather to the front of the engine above the compressor.On vehicles with electric engine mountings, pay attention to correct assignment of connectors at engine mounting and air conditioning system compressor regulating valve N280, as these components have identical connectors. If connectors are interchanged, no fault is stored (components have roughly the same electrical values). Engine mounting is then actuated by operating and display unit, Climatronic control unit J255 and air conditioning system compressor regulating valve N280 by engine control unit.]
4. Unplug connector (A) from mating connector (B) to air conditioning system compressor regulating valve N280.
5. Use adapter cable from adapter setV.A.G 1594 C to re-establish connection between connector (A) and connector (B) to air conditioning system compressor regulating valve N280. [Note: Actuation of the air conditioning system compressor regulating valve N280 and the current measured by the operating and display unit, Climatronic control unit J255 which flows via the air conditioning system compressor regulating valve N280 are displayed in the measured value block of the operating and display unit, Climatronic control unit J255"Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.Use can also be made for this test of an improvised adapter cable. This requires, for example, one connector (A) and (B) each (with part number 1J0 973 702 and 1J0 973 802 and the corresponding plug contacts), two commercially available sockets for banana plugs (C) and two wires with a cross section of 0.5 mm2.]

6. Connect probeVAS 5051/8 to adapter leads.
7. Test lead (signal wire) to contact (2) of connector (A)
8. Test lead (screen, earth) to contact (1) of connector (A)
9. On vehicle diagnostic, testing and information systemVAS 5051 A, set measurement mode: DSO (Digital Storage Oscilloscope) "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
10. Make the following setting on vehicle diagnostic, testing and information systemVAS 5051 A: 5V/div DC, 0.5ms/div (5V DC and 0.5 milliseconds per unit)
11. Start engine.
12. Set temperature for driver's and front passenger's side on operating and display unit, Climatronic control unit J255 to maximum cooling output (e.g. "“Lo”" temperature setting or both rotary temperature controls on "“cold stop”").
13. On the operating and display unit, Climatronic control unit J255, press the buttons Auto, Econ ON/OFF or A/C or ON/OFF for example to activate and deactivate the air conditioning system compressor regulating valve N280.
14. In "“OFF”" or "“Econ”" or "“A/C off”" mode: No square-wave signal (the air conditioning system compressor regulating valve N280 is not actuated)
15. In "“Auto”" mode and "“Lo”" temperature setting: Square-wave signal with pulse width (A) between 75% and 100% (air conditioning system compressor regulating valve N280 is actuated) [Note: The illustration shows a signal with a ratio of approx. 80%.Pulse width (A) is governed by required cooling output, electrical system voltage etc. (over width of area (A), current is controlled via air conditioning system compressor regulating valve N280 by operating and display unit, Climatronic control unit J255).The signal distance (B) is always 2 milliseconds (corresponding to a frequency of 500 Hertz).The signal ratio is derived from the ratio of pulse width (A) to signal distance (B).]
16. Setting on operating and display unit, Climatronic control unit J255 and measured ambient influences govern pulse width of square-wave signal (signal ratio between 100% and greater than 30%, air conditioning system compressor regulating valve N280 is actuated such that compressor output required to obtain specified temperatures is achieved). [Note: In "“Auto”" mode with "“Lo”" temperature setting, for example air conditioning system compressor regulating valve N280 is actuated such that max. perm. current of approx. 0.65 A flows via air conditioning system compressor regulating valve N280 (maximum 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.]

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