Bmw k100rt headlight problem

Here is how they are suppose to work .
Headlamps
The headlamps may be turned on two different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the OFF position, for automatic lamp control (ALC). During ALC, the headlamps will be in day time running lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions. The LH HDLPand RH HDLP fuses, supply battery positive voltage from the underhood junction block to the left and right headlamps. The circuit continues through both low and high beam lamps, then back to the underhood junction block. The low beam and high beam circuits continue to the headlamp switch. The low beam and high beam circuits also provide the body control module (BCM) with both low and high beam inputs. The headlamp switch includes the dimmer switch and the flash-to-pass switch. When the headlamp switch is placed in the HEADLAMP position a path to ground is provided. Ground is provided at G201. Depending on the position of the high/low beam switch, either the low or high beam circuit will now have power and ground.
The LH HDLP fuse in the underhood junction block, supplies battery positive voltage to the automatic lamp control (ALC) headlamp relay coil circuit. The ALC relay switch circuit is connected to the low beam circuit at the headlamp switch. When the headlamp switch is placed in the OFF position, the BCM will automatically turn on the low beams in low light conditions. The BCM energizes the ALC relay, closing the switch contacts and grounding the low beam circuit. Ground is provided at G201. With the headlights in the low beam position, the high beams may be momentarily turned on or flashed with the dimmer switch handle. The flash-to-pass feature is accomplished by pulling the dimmer switch handle toward the driver. The headlights may be switched to high beam with the opposite movement of the dimmer switch lever. When the headlamp dimmer switch handle is pulled toward the driver, the flash-to-pass switch closes grounding the high beam circuit. Ground is provided at G201. Both high beams will remain on until the driver releases the switch handle.
If the driver places the headlight switch in the HEADLAMP position , the headlights will remain on until turned off or the battery runs dead.

Finding a wiring diagram to use along with a DMM - digital multi-meter (voltmeter ) To test the electrical circuits for the headlamps B+ power & ground side of the circuit is the way to find a fix .
Watching a few basic electrical testing video's on youtube may help you .
Basic Electricity for Service Techs Ohm law Current Flow Opens Shorts
How to Use Multimeter to Troubleshoot Common Problems
The Trainer 18 Electrical Testing Tips
Can take years to learn how to trouble shoot automotive electrical systems properly .

I would suspect the handlebar switch for your lights as obviously power is getting through with the passing switch. Make sure the contacts are clean and no wire broken away.

hi Gayle, i would like to help you,i understand that your high beam works and low beam does not.I do not quite understand the flash did you mean hazards?and the word pass?

Common problem, there is a headlight relay in the power distribution center under the hood that needs changed out.

You need a new headlight dimmer switch located on the steering column between the dash and the firewall

The problem will be in the dimmer switch,the contacts are not connecting so the circuit can make the loop for the High,and low beams to work together.

check fuse and relay, if its good, than you have faulty switch, only work on low but not high beam, to turn high beam on the switch move forward which is fauty or no contact, flashing high beam move toward you which has a good contact and working. it two switch in one unit.

Headlight relays..1 for low 1 for high..These are most time under gas tank.Might be also located on battery box

possibly head lamp switch. daytime running lights on separate circuit and use the high beams at reduced voltage. does flash to pass work? that's high beams too. do high beams work?

Is it just low beams?
do taillights work?

Ckeck the headlight connections they are notorious for corroding. Check the ground connection for the lights. Pull your dimmer switch back as if you were flashing a car to pass and see if they work there. If they do you have a dimmer switch problem.