A/C Signal: Description and Operation

Special Tools, Testers And Auxiliary Items
- VAG 1551/1552 Scan Tool With VAG 1551/3 Adapter Cable.
- VAG 1598/18 Test Box
- Multimeter (Fluke 83 Or Equivalent)
- Connector Test Kit VW 1594
- Wiring Diagram

Check Conditions
- Function of A/C OK
- A/C switched off
- Interior of vehicle is at room temperature, above 15°C (59°F)
- No malfunctions stored in Diagnostic Trouble Code Memory.

Test Sequence
- Engine running at idle
- Connect VAG 1551/1552 scan tool and select "Engine Electronics" address word 01.

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-, -0- and -8- for display group 008 and press -Q- button to confirm input.

Indicated on display (1-4 Display fields)

Read Measuring Value Block 8-->
1 2 3 4

- Switch on A/C (lowest temperature and highest blower speed).
- Check specifications for A/C (display fields 3 and 4)




Display Group 008: ECM Signals

NOTE: The A/C compressor will be switched off, when the ECM recognizes full load and the air conditioning is switched on (A/C-HIGH).


Continuation
- If the display does not indicate as described:




- Connect VAG 1598/18 test box to ECM wiring harness.
- Check wiring between test box sockets 37 and 39 respectively and A/C for open circuit according to wiring diagram.
Resistance: Maximum 1.5 ohms

If the specification is not attained:
- Check wiring according to wiring diagram.