Electrical relay
Uses a control signal to switch another electrical circuit.
In a relay or power-distribution location, if separately fitted.
An electromagnetic or solid-state switch controls a load; some functions are integrated into modules.
A small switch operating a heavier-duty switch.
Failure to operate can involve control input, supply, contacts or the powered device.
Batteries and connections depend on age, charging and usage. Control units are diagnosed by faults, power and communications.
A fuse or connection differs from a coded controller. Identify the cause before replacing an expensive electronic module.
A BMW component may use an electronic driver rather than a removable relay.
BMW low-voltage systems across combustion, hybrid and electric models; equipment varies.