How to Replace a Brake Light Switch on a Harley-Davidsonby Chris Gilliland
Modern Harley-Davidson motorcycles rely on many components to provide the style and performance demanded by motorcyclists. While the big V-twin motors have no problem bringing the bike up to speed, they rely on hydraulic brakes to bring the iron steed to a halt. A smaller, yet critical, component to the brake system is the brake light switch which illuminates the tail light when the brakes are engaged. When these switches fail, accidents happen. Fortunately, replacing these switches is well within the grasp of the DIY motorcyclist.
Front Brake Switch Replacement
Check that the ignition is in the "Off" position. For additional safety, disconnect the negative terminal from the battery.
Place your cardboard strip between the front brake lever and the brake switch. This will prevent damage to the switch while removing the switch housing.
Remove the two screws that secure the handlebar clamp to the front brake master cylinder housing, with a Torx T-27 driver. Disassemble the right switch housing by removing two screws, with a Torx T-25 driver.
Remove the screw that secures the brake switch to the housing and cut the switch's wiring. Discard the old switch.
Strip the original switch wiring, exposing 1/4 inch of bare wire. If it is not already prepared, strip 1/4 inch of wire from the new switch's wiring. Cut two separate inch-long strips of shrink tubing and slide them over the new switch's wires.
Twist the ends of each wire from the original harness together with the wires from the new switch and solder to permanently secure the wires. Slide the shrink tubing over the soldered joint and apply heat to seal the tubing.
Hold the brake lever away, place the new switch into the housing and tighten the mounting screw. Place your cardboard strip between the switch and lever before releasing.
Reassemble the switch housing and tighten both T-25 screws to a range of 35 to 45 inch-pounds. Then secure the master cylinder to the handlebar clamp, tightening both T-27 screws to 60 to 80 inch-pounds.
Rear Brake Light Switch Replacement
Check that the ignition is in the "Off" position. For additional safety, disconnect the negative terminal from the battery. Disconnect the switch from the wiring harness by gently pulling off the spade connectors.
Unscrew the switch from the rear brake master cylinder. Clean the switch mounting threads on the master cylinder to prevent contamination of the brake fluid.
Apply a drop of Loc-tite No. 565 to the new switch's threads and install it onto the master cylinder, tightening it down to 84 to 120 inch-pounds. Connect the spade connectors to the new switch.
Turn the ignition switch to the "On" position and depress the rear brake pedal. If the brake pedal feels soft or the brake light does not illuminate, then you may need to bleed the brake lines to remove air bubbles.
- Verify the torque specifications for your specific year and model Harley.
- Take your time. Rushing the repair can create more problems.
- If you are uncomfortable performing this task, or lack the tools necessary for the job, you should have the work done by a qualified technician.
- Do not over-tighten screws or bolts. Over-tightening can damage the threads and lead to costly repairs.
- Use only the Loc-tite compound specified for the application and don't use it where is isn't called for. Using the wrong compound can cause you to strip threads or create a leak at the rear master cylinder pressure switch.
Items you will need
- Carboard strip, 4 millimeters thick
- Torx drivers, T-25 & T-27
- Phillips screwdriver
- Wire cutter and stripper
- Heat shrink tubing
- Heat gun or lighter
- Soldering iron and flux
- Loc-Tite, No. 565
- Torque wrench