Signal From/to A/C Compressor, Checking
Required special tools and test equipment
- VAG1551 or VAG1552 Scan Tool (ST) with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter US1119 (Fluke 83 or equivalent)
- VW1594 connector test kit
- Wiring diagrams
Test conditions
- A/C functions OK
- A/C is switched off
- Vehicle at room temperature above 15 °C (59 °F)
- No malfunctions stored in Diagnostic Trouble Code (DTC) memory. [1][2]Reading Diagnostic Trouble Codes
Checking
- Connect VAG1551 or VAG1552 scan tool and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with engine running at idle). [1][2]Scan Tool Connecting and Initial Checks
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block HELP
Input display group number XXX
- Press buttons -0-, -5- and -0- to input display group number 50 (050), and press -Q- button to confirm input.
Indicated on display (1-4 = display fields)
Read Measuring Value Block 50 ->
1 2 3 4
- Switch on A/C (lowest temperature and highest fan position).
- Compare display with specified values for A/C (in display field 4).
NOTES:
- The A/C compressor is switched off during acceleration when the car is stationary or at slow speed.
- At wide open throttle the A/C compressor is switched off by the Transmission Control Module (TCM) (via the kick down switch).
Continuation
If the displayed values are NOT OK:
- Connect VAG1598/22 test box to ECM harness connector. Connecting VAG 1598/22 Test Box
- Check wiring for open circuit, short circuit to B+ or short circuit to Ground between ECM/test box terminal 8 and either A/C control head -E87- or Transmission Control Module (TCM).
If the wiring is OK:
- Check function of A/C control head -E87-.
- Carry out electrical testing of automatic transmission.
- Check readiness code. Readiness Code Reading
If Diagnostic Trouble Code (DTC) memory has been erased, or ECM was disconnected, generate new readiness code. Readiness Code, Generating