Mercedes Relay - Hella 0025421219

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 Hella

Hella is a German based manufacturer of specialty lighting parts for automobiles and is an OEM (Original Equipment Manufacturer) for Audi, BMW, Mercedes, Mini, Subaru , Toyota, Volkswagen and more. Hella lighting solutions include headlights and fog-lights, complete headlight assemblies, and all the other internal bells and whistles that allow your vehicles lighting system to run impeccably every time you turn the ignition over. One of the most well-known automotive suppliers, Hella ranks highly among the top 50 producers of parts in the entire world and has expanded beyond lighting and into electronics for vehicle interiors. The company was technically founded in 1899, and initially was a producer of candles and lamps for horse drawn carriages. A lot has changed in over 100 years.