A/C System Heat Output and Pump Valve Unit, Checking

A/C System Heat Output And Pump Valve Unit, Checking

NOTE:
- 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 drivers side and front passengers side despite identical setting.
- Corrective action:
- Set air conditioner for drivers and front passengers side to maximum heat output (temperature preselect "Hi") on Climatronic Control Module J255
- Perform long road test at increased engine speed (at least 10 minutes, engine speed greater than 2500 RPM). In doing so, select a low gear to prevent excessive vehicle speed.
- If customer complains of poor heating performance at specific engine speeds, check incorporation of pump valve unit in 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

Special tools, testers and other items required
- Diagnostic operation system VAS 5051 A (or Vehicle Diagnosis Service Syst. VAS 5052)