A/C Compressor Shut-Off, Checking

A/C Compressor Shut-Off, Checking

Special Tools and Equipment







- VAG1526A
- VAG1527B
- VAG1594A
- VAG1598/31
- VAS5051 with VAG5051/1
or
- VAG1551 with VAG1551/3B


NOTE:
- The A/C compressor signal communicates to the ECM that the compressor will be switched on in 140 ms.
- The ECM can switch off the A/C compressor via the same wire connection.
- Engine Control Module (ECM) switches off A/C compressor:
- during hard acceleration (Wide Open Throttle 1st gear)
- in emergency mode (emergency operation)
- after initiating basic setting (function 04)


Test Requirements:
- A/C system OK
- No DTCs in DTC memory of Engine Control Module (ECM).
- Vehicle at room temperature (warmer than +15 °C).

Test Sequence
- Connect VAS5051 tester or VAG1551 scan tool and select the control module for engine electronics using "address word". Refer to "Scan Tool Testing/Scan Tool Connecting And Initial Checks", Testing and Inspection

Engine must run at idle for this.

When indicated on display:


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -8- to select "Read Measuring Value Block" and press -Q- button to confirm input.

When indicated on display:


Read Measuring Value Block Q
Input display group number XXX


- Press buttons -0-, -5- and -0- to select "display group number 050" and press -Q- button to confirm input.

Indicated on display: (1 thru 4 = display fields)


Read Measuring Value Block 50 ->
1 2 3 4


- Switch A/C system off.
- Specified value in display field 4: Compr.OFF
- Switch A/C system on using "Auto" button and adjust A/C system to maximum cooling or heating power. Compressor must run.
- Specified value in display field 4: Compr.ON
- Depress gas pedal completely (swiftly) and then release it (brief acceleration).
- Specified value in display field 4: Indication jumps for a few seconds from "Compr.ON" to "Compr.OFF" (compressor is switched off when vehicle accelerates).

If indications do not resemble description:
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM . Refer to "Scan Tool Testing/Wire And Component Test Using VAG1598/31 Test Box", Testing and Inspection
- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+:

Test box VAG1598/31 Socket A/C control head -E87- Terminal
41

- Repair open circuit or short circuit if necessary.
- If there are no malfunctions in the wiring, check function of A/C system.