Ventilation System Heat Output and Pump Valve Unit Function

Ventilation System Heat Output and Pump Valve Unit Function

If coolant circuit is not completely bled after filling, air may accumulate in heater cores of A/C unit, thus reducing heating performance of air conditioner, additional noises may occur or customer may complain of different air temperatures flowing out of vents at driver's side and front passenger's side despite identical setting.

Corrective action:

- Sent the ventilation system to maximum heat output temperature selector to "Hi" for the driver and passenger sides on the Climatronic Control Module (J255) front A/C control head.

- Perform a lengthy test drive at high engine speed at least 10 minutes, engine speed above 2500 rpm. In doing so, select a low gear to prevent excessive vehicle speed.

• In the event of customer complaints about poor heating output at certain engine speeds, check incorporation of pump/valve unit into coolant circuit. If both coolant hoses supply and return between engine to pump valve unit have been interchanged, engine coolant pump works in opposition to pump in pump valve unit, and at certain engine speeds coolant no longer flows into heater core. Refer to => [ Pump Valve Unit, Checking ] Pump Valve Unit, Checking and

Special Tools and Equipment

• Diagnostic Operation System (VAS 5051 A) (or Vehicle Diagnosis & Service System (VAS 5052))