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


NOTE:
- The A/C compressor signal communicates to the ECM that the compressor will be switched on in 140 ms.
- The Engine Control Module (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 and select vehicle system "01 - Engine electronics". Engine must run at idle for this. Connecting VAS 5051 Scan Tool







Display on VAS5051:
- Select diagnostic function "08 - Read Measuring Value Block" in selection -1-.







Display on VAS5051:
1 - Enter display group Max. input value = 255
- Select function "050" in button field -2- for "display group number 050" and press Q button to confirm input.







Display on VAS5051:
- 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).







Display on VAS5051:
- 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 Engine Control Module (ECM), do not connect ECM. [1][2]Scan Tool Connecting and Initial Checks
- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+:

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

41 -


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