How to Fix a Motorcycle Brake Light Switch

Let's take a look at a very common issue. My brake light stays illuminated even though I'm not actuating, the handlebar master cylinder brake lever, or the rear brake pedal. In this type of housing, the right side housing the throttle side housing. There's a brake switch in the switch housing, and there's actually an actuation point, off of the master cylinder that works with the level. You can open up this housing, and just pull the housing away. Just enough where it'll cause the brake light to come on. The reason for this is that switch in the switch housing is normally in the closed position. When you actuate the lever, the lever allows the switch to move outward, creating a circuit, allowing the brake light to illuminate. Typically, components that are assembled correctly. Don't fail during normal operation. If someone happened to have been in your control housing or your master cylinder recently. And now the brake lights illuminated, chances are the switch is not lined up correctly with the lever. I can take a moment I'll open up the switch housing. I want you to notice I've covered the fuel tank. I've covered the front fender. Anytime you're working above painted or finished surfaces, always cover them. You don't want any damage, in case a tool gets away from you. With the switch housing opened up. I can move the clutch lever assembly with the master cylinder away. And you'll now see that the brake light with the ignition switch turned on, is illuminated constantly. The reason for that, is that now there's no contact against the lever, with the switch holding the switch normally closed. This is the inner portion of the master cylinder on the handlebars. You can see as the lever actuates the brake light tab itself moves inward. Inside the switch housing. There is a small brake light switch. If I were to hold this switch in, with the ignition on the brake light would be off. If I were to release it, the brake light would stay on. Again, these two surfaces, the contact point on the lever and the switch must be in perfect alignment. In order for the switch to operate correctly. What I recommend is inserting a tab, into the master cylinder. That allows the brake lever to remain slightly pulled rearward. When you install it into the switch housing. You'll also note on the master cylinder, that there is a notch, this notch must engage into the tab on the switch housing. I put all the components together loosely. I could actually check to make sure all tabs and notches are lined up. When I installed the outer clamp on the master cylinder. I'll start my threads by hand. I'll make sure most importantly, that the switch housing, and the clamp for the master cylinder are both together tightly. Again, this is a component that you need to use some patience. Make sure all things are lined up. Make sure you're not too far out or too far in on the handlebar, it'll cause binding in the hand grip itself, which is your throttle side. Want to start to draw all your hardware evenly, top and bottom on the handlebar clamp. And also, top and bottom on the switch housings. I've left the tab in the master cylinder hand lever this entire time. It guarantees that the lever is off the face of the switch. And if you weren't turned on the ignition switch the brake light would be on because you're holding a little lever back in an unnatural position when you're riding the lever is normally, all the way out. When you apply the brake you draw the lever back towards the handlebar, that's where I'm simulating with this stopper. When I assemble the switch housings, with the handlebar clamp. You need to make sure that not only are all the components needed together correctly, but also the position of the hand lever in relation to the throttle grip, up and down, is where the rider prefers. Anytime you're doing any type of diagnosis or service in the throttle area. Make sure the throttle screw is completely backed out. Make sure when you're done, your throttle has complete path of travel and returns freely. Once I have the two switch housings, torque to the factory torque spec. Also, the handlebar clamp. Refer to your service manual, there is a torque spec to this. Don't over tighten. Don't under tighten. Chances are if it's loose this assembly you want to rotate, while you're riding, last thing I'll do is remove the stopper. Allow the level to return, all the way out. And at this point you turn on your ignition switch the brake light should be out the brake light should not operate normally. It should be on when the lever is depressed, which means the switch is allowed to move outward and complete the circuit illuminate the brake light. When the lever is released, it will allow the lever to push the switch back inward braking the path of voltage and the brake light should not be illuminated. Again, if the brake light tends to stay illuminated. Even when you verify alignment and correct positioning, all the components, chances are that the end of the switch might have got broken, from being reassembled incorrectly, double check that. If you need to replace the switch, get a replacement switch, put it into the switch housing correctly and follow these steps with the stopper in the lever, when you put the assembly together, and torque it.