Airflow Sensor

The airflow sensor measures the air that goes into the engine through the intake manifold. A small air stream is diverted past two small wire coils. The first wire coil is the temperature measuring coil. This coil measures the air temperature. The second coil is the heating coil. This coil is heated to a fixed level above the normal temperature by the computer. As the diverted air cools the second coil, its resistance decreases. The computer detects the change and boosts the current to the heating coil so that it is restored to the correct temperature and resistance. The amount of current required by the computer to keep the coil at the right temperature indicates the rate of air flow.