In the field of energy, hydrogen as an energetic vector is becoming increasingly important. Specifically, fuel cells powered by hydrogen are becoming an alternative in automotive and other fields because of their ability to produce electricity without any pollution. Therefore, at this time there is a very active research field. A fuel cell can be described as a scale down industrial plant that consists of different subsystems whose purpose is to make the stack works properly. Air Cooled Polymer Electrolyte Fuel Cells (AC-PEFC) are receiving special attention due to their potential to integrate the oxidant and cooling subsystems into one, which in term gives the fuel cells their capability to reduce its weight, volume, cost and control complexity. In these fuel cells, the Oxidant/Cooling subsystem is of crucial importance and along with three others (Fuel, Electrical and Control subsystems) make up the Balance of Plant (BoP), which together with the stack comprise the full fuel cell system. The aim of this paper is to present a comprehensive experimental study of an AC-PEFC paying particular attention to the Oxidant/Cooling subsystem configuration. According to the scientific literature, this subsystem has not received the same attention as other subsystems like the Fuel and Control subsystems. However, a suitable design and size is critical for the proper functioning of the stack. The analysis carried out in this paper tries to solve some problems that can appear if the design of the Oxidant/Cooling subsystem has not been optimized. These problems are related to important aspects such as the performance and the efficiency of the whole system and temperature distribution over the stack. (C) 2018 Elsevier Ltd. All rights reserved.