BMW E34 lights not working: brake lights, headlights and interior lights
Why do the brake lights on an E34 not always come on?
The cause can be the boot wiring harness or the boot lid switch. If the fault is intermittent, a wire or connector is probably faulty. If the brake lights stay on constantly and only go out when you lift the pedal, the fault is in the brake light switch.
Why do the headlights not come on after changing the bulb?
The cause can be the headlight relay, which is inside the light control module (LKM), or a burnt-through wire to the headlight. A cold solder joint on the module can be resoldered with an ordinary soldering iron, taking care to avoid a short circuit.
Why do the interior lights not come on when the door is opened, or stay on?
The door switches may be worn. If only some of the doors do not work, check the wiring connectors: on the touring there is corrosion under the rear seat, on the sedan the connector is in the rear floor next to the central locking wires. Also check the main fuse.
Where do I check if the reverse lights do not work?
Check the reverse light switch, which is on the side of the gearbox. If the switch is fine, check the bulb, fuse and wiring.