A/C Signal: Testing and Inspection

Signal from A/C compressor, checking

Required special tools and test equipment
- VAG 1551 or VAG 1552 Scan Tool (ST) with VAG 155/13 adapter cable
- VAG 1598/22 test box
- Multimeter US 1119 (Fluke 83 or equivalent)
- VW 1594 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.

Checking
- Connect VAG 1551 or VAG 1552 scan tool and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with engine running at idle).Refer to "Scan tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1551/VAG 1552 Scan Tool" Testing and Inspection


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 using the "AUTO" button.
Verify compressor is running.

- Compare display with specified values for A/C (in display field 4).

Display Group 50:

NOTE:
- 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 VAG 1598/22 test box to ECM harness connector.Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1598/22 Test Box" Testing and Inspection
- 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. If Diagnostic Trouble Code (DTC) memory has been erased, or ECM was disconnected, generate new readiness code.
Refer to "Moniters, Trips and/or Drive Cycle (Readiness Codes)/Checking Readiness Code" Testing and Inspection
Refer to "Moniters, Trips and/or Drive Cycle (Readiness Codes)/Generating Readiness Code Testing and Inspection