A/C System Heating Performance, Testing

A/C system heating performance and operation of pump valve unit, testing


NOTE:
- This test covers the operation of the pump valve unit, as well as right and left heat regulating valves -N175- and -N176-, and coolant pump -V50-.
- If a difference from the specifications is found, perform electrical test. A/C System, Electrical Test
- If there are complaints of heating system performance and if during testing, no malfunction of pump valve unit is found, check coolant hoses (from engine and from heater core to pump valve unit) for proper installation.

Test requirements
- The cooling system has been bled according to specifications. Checking:
- All the air guides, covers and seals are in proper order and correctly installed.
- Air flow through the two dust and pollen filters is not restricted.
- The engine is at normal operating temperature, coolant temperature greater than 80 °C (176 °F).

Preparatory work
- Check DTC memory, determine and repair any malfunctions displayed.
- Perform basic setting and check control head coding. Programming and Relearning
- Close front flap and sliding roof.
- Close doors and windows.

Testing
- Connect VAG1551 Scan Tool. Scan Tool Connecting and Initial Checks
- Start engine and run at maximum cooling capacity for a few minutes (compressor is switched on, temperature selector at "LO" for left and right sides).
- Switch ignition off.
- Press "Rest" button (residual heating) on A/C control head -E87-.

A/C control head -E87- operates, coolant pump -V50- does not run, right and left heat regulating valves -N175- and -N176- closed

NOTE: The time for the "Rest" function (residual heating) is limited by -E87- (to about 10 minutes).

- Connect VAG1551 and select Read measuring value block, function 08 (display group 014). Reading
- Read off measured values of display fields 3 and 4.

Specification: ambient temperature plus not more than 15 °C (59 °F)

- Set temperature selector for left side (on -E87-) to "HI".

Specified values:
- Temperature reading of display field 3 increases to approx. engine temperature
- Coolant pump -V50- running, valve -N175- open and valve -N176- closed
- Temperature reading of display field 4 remains approximately constant. Temperature increase less than 10 °C (50 °F) and valve -N176- closed.

- Set temperature selector for right side (at -E87-) to "HI".

Specified values:
- Temperature reading of display field 4 increases to approx. engine temperature.
- Coolant pump -V50- running, valves -N175- and -N176- open

- Set temperature selectors for left and right sides (at -E87-) to "LO".

Specified values:
- Temperature reading of display fields 3 and 4 drop within 5 minutes to ambient temperature, plus no more than 15 °C (59 °F).
- Coolant pump -V50- is not running, valves -N175- and -N176- are closed