The other day a “front brake light switch” message appeared on my 1290’s display. It’s still a pretty new motorcycle. It might even still be under warranty since it’s a 2021 with about 5,000 miles. Anyway, it seemed like it would be a small issue, and I’m a mechanic, and the dealership is far away, so I figured I’d fix it. Now I’m sharing what I found in case you’d like to fix yours.
I have the service manual, which is surprisingly sparse compared to automotive service information. I’m guessing dealerships have electronic service information systems with additional information. After looking at the wiring diagram, my first question was, “How does the control unit (MCU) know that there’s an issue with the brake light switch?” The switch is a single two-wire non-redundant switch. A quick check of the brake light function revealed it still worked, even with the switch unplugged. That means that there must be a pressure sensor in the ABS actuator that measures pressure from the front master cylinder. Many cars are set up that way.
Started with Google
No need to reinvent the wheel. A search for 2021 KTM Super Duke 1290 front brake light switch message brought me to a KTM forum where people said they fixed the issue by cleaning the switch.
Um, no they didn’t. The switch is an Omron microswitch with the markings AQ 09Y9N4 A201, and it’s WAY too tiny (and melted together) for successful repair. (And I do a lot of electronics repair work under a microscope.) But I tried anyway, first with some Deoxit past the switch plunger, then by trying to disassemble it. Was it even bad? Well, it was after I got done trying to disassemble it!
Where to Get a new Switch
A KTM dealer will order a switch for you. Its part number is 61311050000. I ordered one from K&B Motorsports in Petaluma (a good KTM dealer), but it was a week away and the brake light message on the display was annoying me and I can be impatient.
KurveyGirl has Brembo switches that will work. I bought a switch that will function as normally open and normally close depending on how it’s wired (110A-SWITCH-OPEN).
Normally open and normally closed can get a little confusing. For the 2021 Super Duke, the switch is normally open in the diagram. However, you’ll need to buy a normally closed switch. Here’s why that makes sense. If the switch isn’t installed on the bike, and you don’t press the plunger, the switch is closed, so it’s normally closed. However, when the switch is installed on the bike, but front brake lever is pressing on the plunger unless you squeeze the lever, so it’s normally open.
Anyway, the switch arrived two days later. This switch comes with a pigtail, so you’ll need to solder it into your existing wiring. I went ahead and installed it and…. the front brake light switch message comes right back. That’s annoying.
How to diagnose the Brake light switch properly
I suppose I could have stared with this step. And I were working on your car I would have. Anyway, here we are.
Why did it fail so soon?
This motorcycle is less than a year old with only 5,000 miles. Why did the wire break? Many will think it was poorly routed, causing a constant bend or tug, but that’s not it.
There are different types of wire. In your house, where nothing moves, you likely have single conductor wire. It’s stiff like a coat hanger, and if you bend it back and forth enough times it will snap, just like a coat hanger. In automotive applications all wires are multi-strand to allow for flexiblity.
Would I buy another KTM?
Absolutely. I love this bike.
If you’re interested in reading more of my articles (mostly automotive), here’s a link to some of them:
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