Direct injection engines are characterized by improved thermodynamic efficiency (due to the reduction in heat loss via the walls) as compared to injection engines. Coolant passes through the passenger compartment heating system, therefore, in extreme cold conditions, it becomes difficult to reach a comfortable temperature level in the passenger compartment. To reduce the length of the temperature phase increase, vehicles powered by direct injection engines are fitted with heating resistors located directly in the cooling circuit. Electrical power for each water heater component is 300 W. The water heater relay coil is designed to turn on a relay switch, which activates a water heater, monitored by the ECM. The ECM utilizes a water temperature sensor to cut the feed to the water heaters after a specific time period has expired or when the coolant temperature reaches 65℃(149℉). Water supply may also be cut, for a moment, if the battery voltage drops below 10 V. In case of a water heater relay failure, the A/C conditioning system will also experience a water heater deactivation.