A fan drive circuit for a variable speed fan motor in a cooling system, includes an inverter configured to supply a current signal to stator windings of the variable speed fan motor, a frequency detection circuit coupled to an output stage of an inverter of a compressor motor of the cooling system and configured to detect a first frequency of a compressor current signal at the output stage of a variable speed compressor drive circuit and generate a frequency signal, and a digital signal processor (DSP) coupled to the inverter and the frequency detection circuit. The DSP is configured to receive the frequency signal corresponding to the first frequency from the frequency detection circuit, select a second frequency corresponding to the first frequency at which to operate the variable speed fan motor, and transmit control signals to the inverter to supply current to the stator windings at the second frequency.