S4 Sedan L5-2226cc 2.22L DOHC Turbo (AAN) (1992)
/Page-858001.png)
A/C Compressor Signal: Testing and Inspection
Notes:
^
The A/C ON signal increases the basic idle speed to approx. 800 rpm.
^
The A/C compressor ON signal increases the basic value for the Idle Air Control (IAC) valve, ensuring that the IAC valve remains in the center
range of the control map.
^
The A/C compressor cut-out signal switches OFF the A/C compressor for approximately 3 to 12 seconds, when the vehicle is accelerated from a
standing start or a low speed.
Requirements
^
A/C function OK
^
No malfunctions stored in Diagnostic Trouble Code (DTC) Memory
^
Vehicle at room temperature, i.e. warmer than 15°C (59°F)
Procedure
-
Connect VAG 1551 scan tool. Refer to Connecting and Operating VAG 1551 Scan Tool See: Testing and Inspection/Scan Tool Testing and
Procedures/Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting and Operating VAG 1551 Scan Tool
-
Advance through program until display appears as shown:
Rapid data transfer
HELP
Select function XX
-
Let engine idle.
-
Press 0 and 8 buttons to select function 08 "Read Measuring Block Value"
-
Display will appear as shown:
Rapid data transfer
Q
08 Read Measuring Block Value
-
Press Q button to enter input
-
If display appear as shown:
Rapid data transfer
HELP
Input display group number XXX
-
Be sure A/C is switched OFF.
-
Start engine and let idle.
-
Input display group number 05.
-
Observe display values in channel 4.
Display position 1 indicates if A/C compressor is ON or OFF:
^
Must read 0, A/C Compressor OFF
Display position 2 indicates if A/C system is ON or OFF:
^
Must read 0, A/C system OFF
Display position 3:
^
Must remain blank
-
Switch ON the A/C, selecting lowest temperature and highest blower speed.
-
Observe display values.
^
Position 1 must change from 0 to 1
^
Position 2 must change from 0 to 1
-
Observe display while performing the following:
-
Press accelerator pedal to floor quickly, then release immediately.
^
Position 1 must change from 1 to 0, for several seconds
If display position 1 does not change:
-
Connect VAG 1598 Test Box, using VAG 1598/5 adapter cable, to ECM. Refer to VAG 1598 Pin Out Box Connecting and Testing. See: Testing
and Inspection/Scan Tool Testing and Procedures/Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting and Testing VAG 1598
Pin Out Box
-
Connect US 1115 LED tester or equivalent between terminal 19 (GND) and terminal 6.
-
Allow engine to idle.
-
Switch ON A/C, selecting lowest temperature/highest blower speed.
^
LED tester must light up, within 1-6 seconds
-
Apply accelerator pedal quickly, then release immediately.
^
LED tester must go out for a few seconds
