Abstract: A functional module for a coolant circuit of a vehicle fuel cell system includes a container having an ion-exchange material and a pump device for the coolant fluidically coupled to each other in such a manner that a coolant inlet and a coolant outlet of the pump device are connected to a coolant outlet and a coolant inlet of the container. The container surrounds at least one region of the pump device that has a conveying unit of the pump device at least in certain areas around the outer circumference.

Abstract: A coolant circuit (1) for a fuel cell system of a vehicle. Coolant (10) is able to flow through a coolant line (3) in the cooling operation, and an ion exchanger module (4) can be fluidically coupled with the coolant line (3). The coolant circuit (1) has at least one closing element (8), formed to close the coolant line (3). The closing of the same via the at least one closing element (8) is effected by an uncoupling of the ion exchanger module (4) from the at least one coolant line (3). Furthermore, the invention relates to a method to operate the coolant circuit (1).