NOVELTY - The method involves crossing a high temperature air-water exchanger (3) and a low temperature air-water exchanger (4) by flow of air or fluid e.g. glycol water, where each exchanger is supplied by a fluid loop connected with a supply line by the exchangers, respectively. Each loop presents a cooling element, and temperatures (T1, T2) and characteristics of the exchangers. The supply line of the air or fluid flow is separated into two distinct supply lines before energy source, and temperatures of the flow of the supply line is measured after junctioning the two distinct supply lines.    USE - Method for controlling temperature of a flow supply line e.g. air intake line and fluid e.g. glycol water and intake line, using a temperature controlling device of an energy source e.g. fuel cell and battery, in a motor vehicle e.g. electrical vehicle, thermal vehicle and thermal-electrical hybrid vehicle (all claimed).    ADVANTAGE - The method permits controlling of the temperature of the flow supply line e.g. air or fluid intake line, with the energy source embedded in the motor vehicle such that the energy source can operate in optimal conditions under exterior temperatures and lifetime conditions of a fuel cell system, and increases autonomy in the case of the motor vehicle including a battery and the fuel cell or auxiliary energy source in the thermal vehicle equipped with the fuel cell for auxiliary needs.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a device for controlling temperature of air in a flow supply line with an energy source.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a device for controlling temperature of air using a high temperature line and a low temperature line in a fuel cell assembly in parallel mode.'(Drawing includes non-English language text)'    Compressor (A)    Temperatures (T1, T2)    High temperature air-water exchanger (3)    Low temperature air-water exchanger (4)    Heating resistor (5)    Solenoid valve (8)