A/C Compressor Shut-Off, Checking
A/C Compressor Shut-Off, Checking
Special tools and equipment
- VAG1526A
- 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 degree C).
Test sequence
- Connect VAS5051 tester or VAG1551 scan tool and select the control module for engine electronics using "address word" 01. Connecting VAS 5051/VAG1551 Scan Tool
Engine must run at idle for this.
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.
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 to 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) in first gear during a road test and then release it (brief acceleration).
- Specified value in display field 4: Indication jumps for several seconds from "Compr. ON" to "Compr. OFF" (compressor shut-off for vehicle acceleration)
If indications do not resemble description:
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Wiring and Component Testing Using VAG1598/31 Test Box
- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+:
- Test box VAG1598/31 Socket - 41 (Instrument cluster)
- Repair open circuit or short circuit if necessary.
- If there are no malfunctions in the wiring, check function of A/C system.