A/C System Cooling Performance, Testing

A/C system cooling performance, testing

Test requirements
- Radiator and condenser are clean (clean, if necessary)
- Ribbed V-belt is in proper order and correctly tensioned
- All air guides, covers and seals in proper order and correctly installed
- Air flow through the two dust and pollen filters not restricted
- The vehicle is not directly exposed to the sun's rays
- Engine is at normal operating temperature
- With engine running, select the following A/C control head -E87- settings.
- "Auto" mode for driver and passenger sides
- "ECON" button not switched on (compressor switched on)
- "LO" temperature selection (driver and passenger sides)

- A/C compressor is driven (the A/C clutch is switched on)
- Radiator coolant fan -V7- runs (at least in stage 1).
- Fresh air blower -V2- runs at maximum speed.
- The air flow flap closes and recirculating air flap opens (about 1 minute after engine is started).
- The coolant pump -V50- does not run.
- Both left and right heat regulating valves (-N175- and -N176-) are closed (coolant hoses and coolant hoses to the heating system heater cores cool down).


NOTE:
- Testing heating performance of A/C system and operation of pump valve unit.
- If one of the test requirements is not achieved, check DTC memory and perform output Diagnostic Test Mode (DTM).

Preparatory work
- Check DTC memory, determine and repair any malfunctions which are displayed.
- Perform basic setting and check control head coding.
- Close front flap and sliding roof.
- Measure ambient air temperature.
- Close doors and windows.
- Close left and right instrument panel air outlets.
- Close B-pillar air outlets.






- The temperature of the air flowing out of the center instrument panel air outlets must be within the tolerance -C- of the diagram after 5 minutes, depending on ambient temperature.

A - Temperature of air flowing out of the center instrument panel air outlets
B - Ambient temperature measured
C - Permissible temperature range for air outlet temperature

Testing
- Switch ignition on.
- Open center instrument panel air outlets.
- Position thumb wheel for temperature controlled center outlet to "warm".
- Set operating mode to "Auto" and "LO" temperature selection for driver and passenger sides on A/C control head -E87-
- Start engine (compressor is operated).
- Run engine at 2000 rpm (start of time measurement).
- Measure temperature of air flowing out of the center instrument panel air outlets (driver and passenger sides).






Compare measurements with the diagram.


NOTE:
- If the specified values are not achieved, Determining malfunctions if different from specification
- It is good practice to use two separate thermometers for this measurement.
- The temperature of the air in the mixing chambers of the air conditioner housing (downstream of heater core) can be measured with VAG1551 during the A/C system cooling performance test.

Determining malfunction if test results differ from specifications







Continuation from (Testing actuation of pump valve unit)






- Test actuation of left and right heat regulating valves -N175- and -N176-, as well as coolant pump -V50-, testing heating performance of A/C system and operation of pump valve unit

Continuation from (Compressor was switched off during A/C cooling performance test)






- Check DTC memory with VAG1551 Scan Tool, determine and repair all the malfunctions displayed.
- Erase DTC memory.
- Start engine.
- Read measured value block, function 08.
- Select display group 001 and confirm entry with -Q- button.
- Repeat cooling performance test and monitor display field 1 on VAG1551.







Continuation from (Compressor cutoff condition code 1)







Continuation from (Compressor cutoff condition code 3)

- Unplug connector from the A/C refrigerant low pressure switch -F73- and bridge the two terminals of the connector
- Check pressures in refrigerant system
- Repeat A/C system cooling performance test