Compressor HVAC: Testing and Inspection

A/C compressor shut-off, checking


NOTE:
- The A/C compressor signal informs the engine control module that the compressor will be switched on in 140 ms.
- The engine control module can send a signal via the same wire to shut off the A/C compressor.
- The engine control module will shut off the A/C compressor in the following circumstances:
- In emergency running mode (back-up)
- When a signal is received from the Transmission Control Module (TCM) (kickdown switch)
- When the function "Basic Setting" function is initiated (function 04)


Test conditions
- Climate Control functioning properly
- No malfunctions recorded in DTC memory of engine control module
- Interior temperature greater than +15 ° C.

- Connect vehicle diagnostic, testing and information system VAS5051 or VAG1551 scan tool and select engine electronics control module by entering address word "01". When doing this the engine must be idling. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAS5051 or VAG1551" under "Powertrain Management" Testing and Inspection

Indicated on display


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -8- to select function "Read Measuring Value Block" and confirm entry with -Q- button.


Indicated on display


Read Measuring Value Block
Input display group number XXX


- Press buttons -0-, -5- and -0- to select "Display Group 050" and confirm entry with -Q- button.


Indicated on display


Measuring Value Block 50 ->
Input display group number XXX

Display Group 050:

- Check A/C compressor shut-off (display field 4).
- Switch on A/C by pressing the "Auto" button The compressor should run (display field 4).

Display Group 050:

- Set A/C to maximum hot/cold air output (display field 3).
- Switch off compressor with controls on A/C control head.

- Specification for display field 4: The display should change from "Compr.ON" to "Compr.OFF."

If the readout in display field 4 is not as described:
- Switch ignition off.
- Connect VAG1598/31 test box to wiring harness for engine control module. Do not connect to the engine control module itself. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG1598/31 Test Box" under "Powertrain Management" Testing and Inspection

Test the following wiring connections for open circuit and/or short to B+ or Ground (GND).

VAG1598/31 test box, socket Air conditioner, contact
14 -

Resistance in wiring: max. 1.5 ohm
- Repair any open/short circuit as necessary.
- If no malfunctions are identified in wiring, check function of climate control. The readiness code must be generated if the DTC memory was erased.
- Display readiness code. The readiness code must be regenerated if the DTC memory was erased.
Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Readiness Code" under "Powertrain Management" Testing and Inspection
Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Generating Readiness Code" under "Powertrain Management" Testing and Inspection