How to Test a Harley Brake Light Switch
Bob LaRosaDescription
When you pump the rear brake pedal, the rear brake light should tell everyone behind you that you are stopping.
When the rear brake light does not activate, we tend to think it’s the bulb, and sometimes that is not the case.
In this video, Bob walks us through how to test a Harley Brake Light Switch to make sure that’s not the issue.
We also show you how to replace the switch in the housing and Bob reviews The Motorcycle Brake Light Switch here.
Related Videos:
How to Replace Brake Light Switch on a Harley
How to Test a Harley Brake Light Switch
How to Diagnose a Motorcycle Brake Light Switch
Harley Brake Switch Diagnosis Via Manual
Harley Brake Fluid Switch on Sportster
If you update your bars and housing, please watch this video series in full: Handlebars 101
Post:
Let's discuss rear brake light switch function. When you depress the rear brake pedal on your motorcycle, you want your rear brake light to illuminate. Obviously. It needs to be. When the ignition switch is on and the pedal is depressed. The brake light will illuminate. Quick way to check it. You can unplug the two wires that lead to the rear brake light switch. Many switches are in different locations. But all switches land somewhere in the path of the rear brake line. Some may be found upfront off the master cylinder. Some will be found midway like this soft tail. Others, and I've seen them in custom applications. Fall back on the brake line near the banjo bolt that feeds into the rear caliper. On this soft tail, it happens to be just about dead center. Just under the transmission in the brake line. You can carefully remove the two wires with the connectors that go to the brake switch. Now let's say we have no brake light in the back working at all. No matter how hard we push on the brake pedal. Or how many new bulbs we've put in the rear tail light assembly. I want to hook up my test light. The ground side of the test light to the negative side of the battery. Always verify your test light is working by going to the positive terminal on the battery. At that point you can turn your ignition switch. And you can gently probe into the end of the two connectors. One side will always be off. The other side with the ignition switch on should always be illuminated. Again when it come to wiring leave the probe in the connector. Make sure that you move the entire harness around. Make sure you're not getting intermittent connection due to a problem in the harness. And your just blaming it on a bulb or a switch. Once your verify you have good constant voltage. To at least one of the wires going to the rear brake light switch. With the ignition on, you can then take a paper clip. What this test is going to do is going to verify that the rear brake light switch itself is faulty. If you take a paper clip. Fold it evenly into a horseshoe. And again be aware your going to be using 12 volts DC. Don't let this paper clip touch anywhere ground. We can insert it into what we know as the powered side with the ignition on. And verify that it's still getting powered with the test light. Then we can carefully probe into the other connector. Most times when you create a complete circuit like this with a paper clip. You should see a small spark when you plug it into the other end of the wire. With that paper clip causing a complete circuit. Right now this paper clip is acting as a rear brake light switch. You see you've made a complete circuit eliminating the switch. Eliminating any need to depress the pedal. And your brake light should be illuminated all the time. You can verify it by shutting off the ignition switch. Brake light should go out. Turn it on. Brake light is still jumped. We've eliminated the switch. Jumped it with a paper clip. At this point we've verified that we have 12 volts coming to the switch. We've eliminated the switch and jumped it. And we've verified that power goes all the way from the opposite side of the switch. Out into the harness. And feeds the brake light bulb. If you're able to jump theses two connectors the bulb illuminates. It tells you right away the rear brake switch is bad. If you need to replace that rear brake light switch. Be aware you need to be able to access it. You need to be able to tighten it and loosen it. Get Teflon paste on it. It goes into an allocation on the brake line that is a threaded surface. A brake system is a sealed system. You don't want any leaks. You don't want any air left in the system. If you're not confident in doing it. Make sure you get someone who is.
If I hold my front brake lever my brake light comes on if I put my rear brake on the light does not come on is that my rear brake switch that is no good thank you
Could it still be the brake switch if the brake light stays on constantly
Ok , so working out issues on this 1989 FLHTCU I fixed the brake lights , the wires in the left side panel had to be cleaned a soldered then they stopped working again. I did a repeat on the test light still had power to the wires at the switch on the rear. The jim clip test was a fail it made a clicking sound but no break light. The front switch is also not functioning , I did replace the TSM plug and play works fine.I did test the fuses also no problem there , what I did notice the tour pack brake lights stopped working first then the tail light brake light. Sam
<strong> Ticket#11466 Is there a video on how to check a turn signal canceler module ??
1989 ultra , tail lights work but no brake light. Would the same test work ?
Goodridge has a brake light switch that is the banjo bolt as well.
Thank you very much
The rear brake light switch can also fail in the on position. On cruise control equipped models this means that cruise will not engage. Brake lights will also always be on. The always on might be noticable in in a lower voltmeter reading on models equipped with a volt meter. It was in my case, although I put that together after realizing my brake light switch problem in another manner.