To create a steering wheel volume control for a car radio, one option is to connect an electric motor to the existing volume knob, allowing volume adjustments by reversing the motor's polarity. If the radio uses a potentiometer, alternatives include running leads through the dash to install a second pot or purchasing a new stereo with remote capabilities. Installing a small box that translates button presses into infrared signals for the radio is another common method among car stereo installers. For a more complex solution, a microcontroller could be used to manage a digitally controlled potentiometer, though this requires significant effort and expertise. Ultimately, purchasing a head unit with remote control options is often the simplest and most effective solution.