My front brake lever doesn't activate the brake light, but the rear brake lever does. The micro switch and wiring check out fine. There are three wires going into the rear light. I verified the rear running light is getting 12 volts between the brown (negative) and yellow wires. As expected, I get 0 volts between the brown and white wires when neither brake levers are used. However, and this is the weird part, I get 12 volts between the brown and white wires when either brake lever are used. In other words, whenever I'm using the front or rear brake levers, I'm reading 12 volts as expected, but only the rear brake lever turns on the brake light. Can anyone tell tell me how this can be and how to fix it? It's a 2010 690 Duke.
I fixed the issue. I shorted the prongs of the connector at the wiring harness, and the brake lights worked as they should. It turned out to be a bad micro switch. Lessons learned: 1) Even though a micro switch might pass a continuity test, there might be an issue preventing it from working when you supply voltage. 2) My Duke (perhaps other KTM models as well) uses Brembo brakes and levers. They're mostly compatible with Ducati, so I was able to find another micro switch rather easily from eBay.
