Common fault phenomena of relays include: coil burnout, short circuit between turns (insulation aging), contact ablation, thermal decay, and the inability to adjust the initial operating current.
A. The relay coil is burnt out. In order to prevent this from happening, when repairing, maintaining and welding, if the temperature may exceed 80°C, the temperature-sensitive relay and electronic control unit should be removed.
B. Contact ablation. For example, the relay of the air conditioner condenser fan of the Jinbei Hiace car (using the 491Q-ME engine) is just below the glass cleaning spray pipe. If the spray pipe breaks, the cleaning fluid will leak to the relay, making the relay normally open. The contact is rusty and cannot be disconnected, which will cause the failure of the air conditioner condenser fan to run constantly.
Therefore, water should be strictly prevented from entering the relay.