BMW F800GS Headlight Wiring and Relay Diagnostics luxevolume.com

On the F800GS, the headlight circuit is controlled by relays and the handlebar switchgear. If the bulb and fuse are fine, the next step is to determine whether power is reaching the headlight connector at all. Use a multimeter or test light to check for voltage at the bulb socket with the ignition on and the switch in the low-beam position. No voltage suggests the problem lies upstream, in the relay, the switch, or the wiring between them. The F800GS headlight relay can be tested by swapping it with an identical relay from another circuit, or by listening for an audible click when the ignition and switch are activated. A relay that does not click, or that clicks without passing current, should be replaced.