Coolant Recirculation Pump (V50)

Coolant Recirculation Pump (V50)

• The coolant recirculation pump - A - is currently not installed in all vehicles. Check using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.






• Bracket - E - for the coolant recirculation pump and the coolant shut-off valve (N82) or the heater coolant shut-off valve (N279) - F - is not bolted directly to the body in order to reduce noise. To reduce noise, attachment at the bolts is performed with rubber elements. Ensure that these components do not come in direct contact with the body or with other components.

• Depending on the vehicle version and the engine, a check valve can additionally be installed in the coolant circuit. A certain amount of coolant flows through this check valve in the small circuit back to the engine even when the coolant shut-off valve - F -/the heater coolant shut-off valve is activated.

• The installed location of the coolant recirculation pump varies. For most vehicles, it is installed in the plenum chamber as shown in the illustration.

• The activation of the coolant recirculation pump varies. For most vehicles, the Climatronic control module (J255) is activated directly by the front Climatronic control module A/C display and control head.

Function

• The coolant recirculation pump - A - supports the engine's own coolant pump during coolant recirculation. It is activated by the Climatronic control module (J255) to ensure sufficient and even coolant flow through the heater core(s) of the A/C system. Check using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

• When the coolant recirculation pump - A - is on, the coolant is drawn in by the engine via coolant hose - C - and is pumped via coolant hose - D - to the heater cores of the A/C units. Via the heater cores in the A/C units (front and rear) and the coolant shut-off valve/the heater coolant shut-off valve (depending on the engine version and the vehicle equipment), it flows back to the engine, refer to => [ Incorporation of A/C System in Coolant Circuit ] Incorporation of A/C System in Coolant Circuit.

• The coolant recirculation pump - A - is activated directly when the ignition is turned on and depending on the coolant temperature and the setting on the Climatronic control module. Check using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function and.

• Depending on the vehicle version, the coolant recirculation pump- A - is also activated by the Climatronic control module when the parking heater is on or in the residual heat function. Check using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

• The coolant recirculation pump - A - (and the coolant shut-off valve) are also activated directly by the Climatronic control module in vehicles with a Start-Stop system. If present, the heater coolant shut-off valve is also activated via the auxiliary heater control module (J364) by the Climatronic control module. Check using and the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

• If any malfunctions in any of the components in the Climatronic control module, are stored, check the version, coding and adaptation of the Climatronic control module using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

• Removal and installation, refer to => [ Coolant Recirculation Pump (V50) ] Service and Repair.

• Remove and install bracket - E - for the coolant recirculation pump and the coolant shut-off valve/heater coolant shut-off valve, refer to => [ Bracket For (V50) and (N82) ] Bracket For (V50) and (N82).