Introducing an electric thermostat to the thermal management system is a way of actively controlling the temperature of the engine, which has been shown to have several possible gains regarding power, fuel consumption, emissions and engine durability. Complexity, cost and durability are key concerns that have led to no heavy duty truck on the market having an electrically controllable thermostat. This emphasizes the need for exploring alternative solutions that enables electric control of the thermostat according to the needs of heavy commercial vehicles. Several concepts have been generated to solve this problem and a model based approach in Simulink, Matlab and GT Suite was used for the development and evaluation. The most promising concept of combining a BLDC electric motor with a wax body enables electric control with a downsized actuator and full fail-safe function while showing improvements in temperature control performance compared to a traditional wax thermostat. This thesis has increased the knowledge on the subject and could allow for implementing an electrically controlled thermostat in future Scania heavy duty trucks, leading to a more durable engine with lower fuel consumption and emissions.