Engagement signal for A/C Compressor Regulator Valve N280, checking

WARNING: This page is about a different car, the 2008 Audi S4, 2008 Audi RS 4, and 2008 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.

Switch off ignition.
Connect operating and display module, Climatronic Control Module J255 to vehicle wiring harness.
Disconnect connector at air conditioner compressor (to A/C Compressor Regulator Valve N280).

Fig 1: Using Adapter From Connector Test Set V.A.G 1594C To Reestablish Connection Between Connector & Connector At Compressor

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Use adapter from Connector Test Set V.A.G 1594C to reestablish connection between connector - A - and connector - B - at compressor (to A/C Compressor Regulator Valve N280).

Fig 2: Identifying Connectors & Sockets For Banana Plugs

Courtesy of VOLKSWAGEN UNITED STATES, INC.

NOTE:

Use can also be made for this test of an improvised adapter. 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 mm ² .

Connect Dso Measuring Leads 1 2 VAS 5051/8 to adapter leads.
Measuring lead (signal wire) to contact 2
Measuring wire (screen, Ground (GND)) to contact 1
On Diagnostic Operation System VAS 5051A, set measurement mode: "DSO" (Digital Storage Oscilloscope).

Settings 5V/div DC, 0.5 ms/div (5 V DC and 0.5 milliseconds per unit)
Start engine.
On operating and display module, Climatronic Control Module J255, select "Lo" temperature setting for drivers and front passengers side.
On operating and display module, Climatronic Control Module J255, press buttons "Auto" and "ECON" to activate and deactivate A/C Compressor Regulator Valve N280.

Display on oscilloscope screen will be as follows depending on setting on operating and display module, Climatronic Control Module J255 :

In "OFF" or "ECON" mode: no square-wave signal (A/C Compressor Regulator Valve N280 is not activated)

Fig 3: Oscilloscope Screen Display

Courtesy of VOLKSWAGEN UNITED STATES, INC.

In "Auto" mode and "Lo" temperature setting: Square-wave signal with pulse width - A - between 75% and 100% (A/C Compressor Regulator Valve N280 is activated)

NOTE:

The illustration shows a signal with a ratio of approx. 80%.
The pulse width - A - is governed by the required cooling output, electrical system voltage etc. (over width of area - A -, current is controlled via A/C Compressor Regulator Valve N280 by operating and display module, Climatronic Control Module J255).
The signal distance - B - is always 2 milliseconds (corresponding to a frequency of 500 Hertz).
The duty cycle is derived from the ratio of pulse width - A - to signal distance - B -.

The setting on the operating and display module, Climatronic Control Module J255 and measured ambient influences govern the pulse width of the square-wave signal (signal ratio between 100% and greater than 30%, A/C Compressor Regulator Valve N280 is activated such that the compressor output required to obtain the specified temperatures is achieved).

NOTE:

In "Auto" mode with "Lo" temperature setting, the A/C Compressor Regulator Valve N280 is activated such that the max. perm. current of approx. 0.6 to 0.8 A flows via the A/C Compressor Regulator Valve N280 (maximum compressor output).
In control mode, the activation time is governed by the 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.