For the connector of the power transistor that controls blow fan airflow, it is not installed in the right place, and the terminal surfaces are not properly processed. The contact points of the connector may fail to touch each other fully after the connector is pushed by external force, e.g. by a passenger's foot, and the resistance of the contact points may increase, causing the temperature of the connector to rise. If this is repeated, the connector may be damaged by melting, and in the worst case, the blow fan could malfunction, making the defroster inoperable.