Most of automotive industry companies find out that the results obtained from the tests of the whole cooling system do not match the expected ones, taking into consideration the particular characteristics of each component of the system. Facing this controversy, the importance of testing also the components individually is growing every day and has become indispensable. In pursuing this goal the market has been studied and the important theoretical concepts, which are necessaries to understand the main function and characteristics of the cooling system, have been explained. As a result the solution chosen is a small open-circuit wind tunnel. Also the sensors used have been defined in order to register the measures needed to make the test and the total error obtained for the propagation of uncertainty. It is worth noting the importance of the sensors’ accuracy, which is a key aspect in the calculations mentioned; the difficulty found working in the air side, because its behaviour is quite unpredictable; and, finally, the need to create a simulation model with Computational Fluids Dynamics in order to know how they move inside the wind tunnel.