Checking Operation of Pump Valve Unit

Checking Operation Of Pump Valve Unit

This test is used to check operation of pump valve unit (Left Heat Regulating Valve N175 and Right Heat Regulating Valve N176 as well as Coolant Pump V50).

- If temperatures determined are below specified value (inadequate heat output):
- Check operation of Left Heat Regulating Valve N175, Right Heat Regulating Valve N176 and Coolant Pump V50 "Guided Fault-Finding" function of Diagnostic Operation System VAS 5051.

If no malfunction is found:
- Check for interchanged coolant hoses (from engine to pump valve unit or from pump valve unit to heater cores of air conditioner unit) and 4.2 Liter V8 5V Engine Mechanical, Engine Code(s): BFM or 6.0 Liter 12-Cyl. 4V Engine Mechanical, Engine Code(s): BSB.
- Check for interchanged electrical contacts of Coolant Pump V50 of pump valve unit (direction of pump operation)

Test requirements
- Coolant circuit bled in specified manner 4.2 Liter V8 5V Engine Mechanical, Engine Code(s): BFM or 6.0 Liter 12-Cyl. 4V Engine Mechanical, Engine Code(s): BSB
- All air ducts, covers and seals OK and properly installed
- Air throughput of dust and pollen filter not impaired by dirt
- Engine warm
- Vehicle battery - A - OK and adequately charged (to prevent Energy Management Control Module J644 switching off Climatronic Control Module J255 during test)
- DTC memory of Climatronic Control Module J255 (Rear A/C Control Head (Climatronic) E265) checked and erased, basic setting performed and coding of Climatronic Control Module J255 checked Climatronic Control Module J255, Coding (Function 07) and "Guided Fault-Finding" function of Diagnostic Operation System VAS 5051
- Adaptation of Climatronic Control Module J255 (and Rear A/C Control Head (Climatronic) E265) checked Adaptation (Function 10) "Guided Fault-Finding" function of Diagnostic Operation System VAS 5051
- Vehicle not exposed to sunlight

Checking
- Close hood.
- Close doors, windows and sun roof.
- Start engine and let it run for a few minutes at maximum cooling output (compressor ON, "LO" temperature setting for left and right side).
- Switch off ignition.
- With ignition off, connect Diagnostic Operation System VAS 5051A with Diagnostic Cable - 3 meter VAS 5051/5A to 16- pin diagnostic socket in vehicle and use address word "08" to select air conditioner/heater electronics
- Switch on ignition.

Front operating and display unit starts up, Coolant Pump V50 is not actuated and does not run, Left Heat Regulating Valve N175 and Right Heat Regulating Valve N176 are actuated and closed.

- Read out measured value block, display groups "034" and "035". Energy Management Control Module J644 must not have effected shutoff "Guided Fault-Finding" function of Diagnostic Operation System VAS 5051A.
- Read out measured value block, display group "017" "Guided Fault-Finding" function of Diagnostic Operation System VAS 5051A.
- Check display in zones "1" and "2".

- Specification: Ambient temperature plus max. 15 degrees C
- Set temperature for left side (drivers side) on front operating and display unit to "Hi".
- Read out display in zone "1" (temperature value increases).

- Specification: approx. engine temperature (operation of Coolant Pump V50, Left Heat Regulating Valve N175 open)
- Read out display in zone "2" (temperature value remains roughly constant).

- Temperature increase less than 15 degrees C (Right Heat Regulating Valve N176 closed)
- Set temperature for right side (front passengers side) on front operating and display unit to "Hi".
- Read out display in zone "2" (temperature value increases).

- Specification: approx. engine temperature (operation of Coolant Pump V50, Left Heat Regulating Valve N175 and Right Heat Regulating Valve N176 open)
- Set temperature for drivers and front passengers side on front operating and display unit to "LO".
- Read out display in zones "1" and "2".

- Specifications: Temperature drops within 5 minutes to ambient temperature (plus max. 15 degrees C) (no operation of Coolant Pump V50, Left Heat Regulating Valve N175 and Right Heat Regulating Valve N176 closed)