Additional coolant pump

Additional coolant pump

The coolant pump is an integral component of the coolant circuit and thus part of the heat exchanger system. It is located in the coolant feed in the direction of flow before the temperature sensor of the coolant feed. The speed of the coolant pump has a direct influence on the temperature of the withdrawn hydrogen via the heat exchanger system. This speed control is map-controlled.

The pump communicates with the CESG via the BSD interface.

The additional coolant pump is monitored for diagnosis.

During the phase of vehicle use, the additional coolant pump can be in five possible states:

• ”Stop”: Pump speed is 0 and there is no emergency operation.
  
• ”Control”: In this state, the pump is map-controlled.
  
• ”Regular after-run”: This state is only active during after-run. The speed monitoring of the pump is then switched off.
  
• ”Icing after-run”: This state is necessary to promote de-icing of the coolant circuit.
  
• ”Ventilation”: This state can only be used for service purposes to ventilate the coolant circuit.
  
• ”Pump active”: Summary of all states where the pump turns.
  

Component diagnosis

Detectable faults are present if there are transmission and communication faults, pump-specific faults or thermostat faults (overheating). Within the framework of the test modules for this function group, the following faults are covered:

• 64DA control thermostat
  
• 64B9 output circuit, auxiliary water pump