Audi Mercedes Porsche VW Multi-Purpose Relay - Bosch 0025421119

Product Information

A multi-purpose relay is an electrical switch that uses a small electrical current to control a larger current electrical circuit. The function of a relay is to activate various systems or functions that use a high electrical current without requiring high-current wiring directly running through the switchgear or ECU. The relay consists of a coil and a set of contacts. When a small current energizes the coil on the low current side, it creates a magnetic field that flips the switch back and forth, closing or opening the contacts and completing or breaking the circuit that powers the high-amperage device.

Multi-purpose relays are generalized relays that can run a number of different types of systems, such as fuel pumps, cooling fans, lighting, HVAC components, and windshield wipers just to name a few. This is why you will notice a multi-purpose relay may be listed for several different applications within a car, or the same application across multiple vehicles.

To diagnose a relay, you can energize the low current side using a basic 12v signal. You will hear the relay clicking. If the click is inconsistent or dulled, it might not be making a good contact. When it clicks, a multimeter should show continuity and near-zero resistance between the high-current contacts. If not, then the relay may be bad. Basic multi-purpose relays are very simple devices, so they don’t usually fail. However, if the relay has been subjected to extreme temperatures, or weather exposure, or is very old, never rule out a bad relay causing problems in your electrical system.

• System Failure: Several systems use multi-purpose relays to power them. When a relay goes bad, those systems will intermittently work or fail. A proper electrical diagnosis with a multimeter, or swapping the relay with a known good one is the best way to fix a failed relay.

About Bosch

Bosch is one of the worlds leading suppliers of engine electronics and sensors. Their sensors and modules can be found in almost every modern car on the planet. Bosch Automotive offers a comprehensive portfolio of unmatched solutions for every job. From diverse diagnostic solutions and OE-quality auto parts, to industry-leading software and unmatched vehicle coverage, to innovative charging, repair and maintenance tools. Making repair and maintenance more effective, efficient, and sustainable for the vehicles of yesterday, today and tomorrow. With over 130 years of experience in the automotive industry, Bosch continues to lead the way in automotive innovation by inventing and developing quality products and solutions that focus on customer needs, shaping the future, and the continued pursuit of excellence.

Robert Bosch founded the “Workshop for Precision Mechanics and Electrical Engineering” in Stuttgart, Germany in 1886. Since the beginning Bosch has been a leader in innovation and development. They introduced fuel injection into mass production in 1967 laying the foundation for modern ignition electronics. Bosch brought lambda sensors to market in 1976, paving the way for cleaner exhaust gases and better fuel economy.

With millions of parts and products in their product line, Bosch offers everything from brake pads to household tools and medical supplies. FCP Euro has partnered with Bosch for the 2019 TC America Championship. They are a sponsor on our 2018 Volkswagen GTI TCR race cars. We offer Bosch's full line of OE and OEM components for your European vehicle.