K100RS Brake Light, Warning light and Switch headache

Hello All: I am wondering how many players are involved in achieving a brake light and getting the warning lamp on the instrument cluster going off. I have been experiencing a loose gremlin in my brake light and warning lamp system for several months. I have replaced the switch at the brake hand lever (front brake). My current symptom is:
Brake lights work when the foot pedal is pressed but not when the hand lever is used.
The warning light does not extinguish. The warning light modulates a bit when the foot pedal is pressed but not when the hand lever is engaged.
The brakes work fine.

Having replaced bulbs and the switch I am not sure what other component of this devilish system can be replaced...

Any suggestions?

Make sure your rear tail light/running light bulb is working. If it is burnt out the red warning light will come on.

Test each switch.

Rear:
1. Remove the frame right-hand side cover.
2. Disconnect the electrical connector going into the rear brake light switch.
3. Use an ohmmeter or continuity tester and check for continuity between the 2 terminals on the brake light switch. There should be no continuity (infinite resistance) with the brake pedal released. With the brake bedal down or applied there should be continuity (low resistance). If the switch fails either of these tests the switch must be replaced.

Front:
Do the same with the front brake lever and switch with the connector underneath the gas tank.

sgtbill said:

Hello All: I am wondering how many players are involved in achieving a brake light and getting the warning lamp on the instrument cluster going off. I have been experiencing a loose gremlin in my brake light and warning lamp system for several months. I have replaced the switch at the brake hand lever (front brake). My current symptom is:
Brake lights work when the foot pedal is pressed but not when the hand lever is used.
The warning light does not extinguish. The warning light modulates a bit when the foot pedal is pressed but not when the hand lever is engaged.
The brakes work fine.

Having replaced bulbs and the switch I am not sure what other component of this devilish system can be replaced...

Any suggestions?

Click to expand...

The simple answer is to try a new bulb monitor inside the relay box under the gas tank.
If that doesn't fix it, or you don't want to buy one first, then...
At the switch connector where it goes to the bikes wiring there are two wires. One is green/blk and one is gray/red. The green/black wire has +12 volts on it all the time. If there is no +12 on the green/black wire, you will have to trace where it is broken. It goes to a connector for additional instruments, fuel level and temp gauge. Check for +12 there. If Not +12 there then the green/black goes to a bundle of wires inside the wiring harness. You would have to find that bundle and investigate. Or run a new wire for the green/black connection to the switch.
If you do have the +12 on the green/black at the switch connector, then measure the gray/red wire for voltage when the switch is actuated. When the switch is actuated the gray/red wire goes postitive to +12 volts. That wire ends up at the bulb monitor in the relay box. If you get +12 volts at the switch connector, then you have to see if you get +12 at the other end of the gray/red wire going into the bulb monitor module. That is pin #3 on the bulb monitor connector. If you get the +12 there, then I would guess you need to try a new bulb monitor module. If you are missing the +12 anywhere along this testing, then the break is between where you last had +12 and where it was not.
This is actually easier to do than write about...

cjack said:

The simple answer is to try a new bulb monitor inside the relay box under the gas tank.
If that doesn't fix it, or you don't want to buy one first, then...

This is actually easier to do than write about...

Click to expand...

So I could also just buy the bulb monitor that goes into the relay box under the tank? That seems pretty straight forward. I already have many hours of annoyance invested in this problem. At my billing rate in a couple weeks I will have enough to pay for a new one. My aggravation has a value (or cost). I think I'll give the new bulb monitor a try. In either case I will have to wait until after Thanksgiving to work on it. The salt mine that is my job calls...

Thanks for the replies.

sgtbill said:

So I could also just buy the bulb monitor that goes into the relay box under the tank? That seems pretty straight forward. I already have many hours of annoyance invested in this problem. At my billing rate in a couple weeks I will have enough to pay for a new one. My aggravation has a value (or cost). I think I'll give the new bulb monitor a try. In either case I will have to wait until after Thanksgiving to work on it. The salt mine that is my job calls...

Thanks for the replies.

Click to expand...

Yes. That bulb monitor may be at fault. I haven't heard of many of them going bad, if you are under the tank and measure that grey/red wire and get the +12 at pin #3 when engaging the hand brake, then it's likely that it's the problem. Otherwise, it's the tracing of the wires job.