BMW Carrier Relay - Genuine BMW 12901747915

Product Information

BMW Relays diagram for 740i, 740iL, 750iL

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 Genuine BMW

The original parts used by BMW to build your car are available as replacement parts under the “Genuine BMW” brand. When ordering a Genuine BMW part you are guaranteed to get the same part that you would pick up from your local dealerships part department. Genuine BMW parts have been built to BMW’s stringent standards and are the same quality of the original parts used to build your Ultimate Driving Machine.

You may not realize this, but the parts that make up your BMW are not necessarily manufactured by BMW. No cause for concern, as BMW designs the part, hires a manufacturer, and ensures its quality to you. In fact, many of these manufacturers have been making parts for BMW for decades. In our industry these manufacturers are called OEM (Original Equipment Manufacturers), and these are often brands you recognize, including Lemforder, ZF, Sachs, Bosch, Valeo, Zimmermann, Siemens VDO, Corteco, and more. Don’t be surprised to open that Genuine BMW parts box and find an OEM branded part inside, simply with the addition of a BMW logo.

Be sure to keep an eye out for OE tags on our product pages to quickly identify parts coming direct from OE manufacturers. That extra bit of insight could save you some serious money while shopping! Refer to our OE Academy for further information regarding the OE/OEM tags throughout the site.