Mercedes W204 Genuine Universal Car Relay 4-Pin Hella Black A0025421319

Mercedes W204 Car Relay 4-Pin Hella Black A0025421319 is a component from the Electronic Control Units and Controllers group, designed for use in the electrical systems of Mercedes vehicles. Its compact, black housing and 4-pin connector configuration allow for stable control of selected electrical circuits, ensuring predictable operation of onboard systems.

Specifications and technical data

• SKU: A0025421319-1
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A0025421319
• Substitutable numbers: A0025421319, A 0025421319, A 002 542 13 19, ASZ
• Color: Black
• Category: ECUs & Computer Modules

Relay Purpose and Function

This Hella car relay is designed for the electrical systems of Mercedes W204 models, where it is responsible for switching higher-load circuits using a low-current control signal. Its 4-pin configuration enables classic on/off switching, a common solution in many auxiliary vehicle circuits.

Its placement in the Electronic Control Units and Controllers category highlights its role as an actuator within the power management system, collaborating with ECU control modules, fuse boxes, and other onboard electronics components.

Construction and Design Features

The relay features a compact, black housing that facilitates identification within the relay box and aesthetically complements other installation components. The standard 4-pin terminals allow for installation in typical sockets used in Mercedes vehicles, promoting hassle-free component replacement during servicing.

The solution, based on proven Hella technology, ensures repeatable performance parameters, and its automotive-grade construction is adapted for operation in varying temperatures and typical engine bay vibrations.

Integration with Mercedes Electrical System

The relay is designed to work with the factory Mercedes W204 wiring harness, simplifying the maintenance of the original installation architecture. This allows for consistency with service documentation and vehicle wiring diagrams, ensuring that diagnostics of potential faults remain clear for service personnel.

This component can be used as a replacement in applications requiring a 4-pin relay with similar operating characteristics, provided there is electrical and mechanical compatibility with the socket and the requirements of the specific circuit.

Product Condition and Service Application

The offered relay is a used component, making it an attractive service solution for situations where cost optimization is key while maintaining original manufacturer specifications. Such components are often chosen for routine repairs, electrical system fault diagnostics, and replacement of damaged relays in fuse boxes.

In workshop practice, this type of relay is used both as a direct replacement part and as an auxiliary component for testing – for example, to verify whether a circuit problem stems from a faulty relay itself or another part of the installation.

Selection, Compatibility, and Technical Support

Due to the presence of a dedicated part number and available replacement numbers, it is always advisable to confirm the correct relay for a specific vehicle configuration based on service documentation or markings on the original component. If in doubt, comparing the electrical parameters and pin layout with the previously installed relay is helpful.

If you want to better understand how to safely use used onboard electronics, including modules and sensors, you can find practical tips in the Global Parts guide: Used Car Electronics Onboard – Why Choose Second-Hand ECUs and Sensors?

If you are planning a comprehensive repair or upgrade of the electronics and control area in your Mercedes and need other components from the same group, such as control modules, relays, or auxiliary controllers, check the available parts in the Mercedes Electronic Control Units and Controllers category.