Checking Heat Output of Air Conditioner and Operation of Pump Valve Unit

Checking Heat Output Of Air Conditioner And Operation Of Pump Valve Unit

NOTE:
- If coolant circuit is not completely bled after filling, air may accumulate in heater cores of air conditioner unit and thus reduce heat output. In addition, noise may occur or complaints may be received about differences in temperature of air from drivers and front passengers vents despite identical setting.

- Remedy: -
- At Climatronic Control Module J255, set air conditioner to maximum heat output ("Hi" temperature) for drivers and front passengers side.
- Perform lengthy test drive at high engine speed (at least 10 minutes, engine speed above 2500 rpm). In doing so, select low gear to prevent excessive vehicle speed.
- In the event of complaints about poor heat output at certain engine speeds, check incorporation of pump valve unit into coolant circuit. If the two coolant hoses (supply and return) between engine and pump valve unit have been interchanged, the engine coolant pump works in opposition to the pump in the pump valve unit and at certain engine speeds coolant no longer flows into the heater cores 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.

Special tools, testers and other items required

- Diagnostic Operation System VAS 5051A (or Vehicle Diagnosis and Service System VAS 5052)