Since there has been facing with global warming and exhaustion of natural resources, development of eco-friendly vehicles was paid attention from many people globally. Among various designs and technologies on the current market, the most eco-friendly vehicle would be electric vehicles. As electric vehicle doesn''t have engine being a heat resource on a vehicle, there was a new demand for heater to warm up the inside of vehicle instead of heating using engine, so that high voltage (HV) PTC (Positive Temperature Coefficient) heater was developed as a solution. In order to keep the equivalent heating capacity with the heating capacity of vehicles which use fossil fuel energy, HV PTC heater needs lots of power to sustain more than 5 kW of heat capacity. By using HV PTC heater, electric vehicles caused a short driving distance with one-time charge. For achieving this purpose, active controlling technologies for HV PTC heater are developing to cover the short driving distance issues. Currently, PWM(Pulse With Module) is applied for a recent technology to control HV PTC heater. As monitoring the vehicle battery status in regular basis, it controls and optimizes the inside temperatures of vehicle and increases the feasibility of vehicle driving efficiency. Even though PWM technology is commonly used in most of industries, a vibration created from PTC stone itself leads abnormal noise problems because PWM signals control PTC stones in switching. In recent, HV PTC heaters was developed to use low PWM switching frequency in order to have lower noise level than a noise of blower motors installed on HVACs. From the analysis here, it was found that the switching frequency was in proportional to the noise level. As the results of the research, a mechanism was found able to reduce the abnormal noise from PTC stones with vibration.