Volvo ship engine starting relay 874743

During the long-term use of Volvo ship engines, the starting relay 874743 may encounter various faults that affect the normal starting of the ship engine. Below, we will provide a detailed introduction to some common faults and their solutions.

Contact erosion: This is one of the most common faults. Due to the high current during startup and frequent opening and closing of the contacts, the surface of the contacts is prone to burn marks and become uneven after prolonged use. When the contact is severely eroded, it will cause an increase in contact resistance, and a large amount of heat will be generated when current passes through, further exacerbating the degree of erosion, which may ultimately lead to the circuit not conducting properly and the ship engine not starting.

Inspection method: Open the relay housing and carefully observe the contact surface. If there are obvious black burn spots, pits, or the contact surface is no longer smooth and flat, it indicates that the contact has been burned.

Solution: For slightly eroded contacts, you can use fine sandpaper to gently polish the eroded part to restore good conductivity. When polishing, pay attention to even force to avoid excessive polishing that may cause thinning of the contact points and affect the service life. After polishing, wipe off any metal debris on the contact surface with a clean cloth. If the contact is severely eroded and polishing cannot solve the problem, it is necessary to replace the new contact or the entire relay to ensure the reliability of the circuit connection.

Coil short circuit: When the electromagnetic coil of the relay is short circuited, it will cause the coil resistance to decrease and the current to increase. This not only prevents the relay from working properly, but may also cause overheating, even burning out the relay, and in severe cases, it may also affect the normal operation of other circuits in the ship's machinery.

Solution: Once it is determined that the coil is short circuited, due to the difficulty of repairing the coil and the difficulty in ensuring its performance after repair, it is usually recommended to directly replace the relay with a new one and choose a product with the same prototype number to ensure compatibility and performance matching.

Poor contact of contacts: In addition to erosion causing poor contact, long-term vibration, corrosion, and insufficient contact pressure may also cause the contacts to not fit tightly during operation, resulting in circuit on-off. This can lead to unstable start-up of the ship's engine, sometimes it can start and sometimes it cannot, causing great difficulties for water operations.

Inspection method: When the relay is working, gently shake the relay by hand and observe whether there is any change in the starting status of the ship's engine. If the ship's engine starts abnormally during the shaking process, such as suddenly shutting down or interrupting the start, it is likely due to poor contact of the contacts. In addition, a multimeter can also be used to measure the resistance when the contact is closed. Under normal circumstances, the resistance should be close to zero. If the resistance is high, it indicates that there is a problem with the contact.

Shell damage: The working environment of ship engines is complex, and the shell of relays may be damaged due to collisions, aging, and other reasons. After the shell is damaged, it not only exposes the internal parts and makes them vulnerable to dust, water vapor, and other erosion, affecting the performance and lifespan of the relay, but also may pose safety hazards, such as the risk of electric shock.