A capacitance sensing system for sensing frost and ice accumulation. The capacitance sensing system comprises a first capacitor formed by a portion of a metal heat exchanger and a sensor electrode electrically isolated from the metal heat exchanger, a tank oscillator comprising a second capacitor and an inductor connected in parallel with each other and coupled in parallel with the first capacitor, and a circuit coupled to the tank oscillator. The circuit coupled to the tank oscillator is configured to determine a resonant frequency of the tank oscillator, determine a capacitance value based on the resonant frequency of the tank oscillator, determine that the capacitance value is greater than a predefined threshold, and transmit a heater activation command in response to determining the capacitance value is greater than the predefined threshold.