In a cooling system having a plurality of identical cooling circuits, fault detection is determined by a controller if monitored operating parameters of the cooling circuits differ from each other by an appreciable amount. In an aspect, the controller uses a comparison of the operating parameters of a cooling circuit to a snapshot of the operating parameters of that cooling circuit taken after the cooling circuit is determined to be operating properly after start-up. In an aspect, the controller uses known operating parameters of a cooling circuit and a system model of the cooling circuit to calculate remaining operating parameters of the cooling circuit (system model operating parameters) and uses a comparison of the system model operating parameters to the monitored operating parameters.