Howdy fellas. I just had the front end torn down to rebuild my front forks. Everything is back together and I’ve discovered that my brake light isn’t working right anymore.

When I turn the ignition switch on, the running light is on. Then if I push either brake, the brake light comes on and won’t turn back off. If I turn the ignition switch off and back on, the running light is on but brake light is back off until I push a brake again. I’ve taken the master cylinder off and operated the handlebar switch by hand to check if the lever was the culprit but I’m getting the same results.

Any ideas? Thanks in advance

 

Try replacing the rear brake light switch or remove rear caliper, disassemble and clean it then flush the system, refill and bleed.

 

Front brake switch is a plunger type switch off the lever when it pulled back.

Rear brake switch is a pressure switch in line on the rear brake line.

Both activate the brake light relay.

So start by pressing on the rear brake peg, and see if the brake light is working correctly to start with.
Next, pull the front brake lever and see if it working correctly. Note, make sure to push the lever all the way open to see if that solves the problem,
If the problem is the front lever plunger switch, may have screwed it up the front brake light switch when you put the lever back on.

As for brake relay, could be sticking and needs to be replaced, but since you where working on the front end alone, by guess is that you did not put the lever back on correctly, and broke the front brake switch.

 

I sheared off the front brake switch a couple years back on my 96 raodkng.The manual says put a shim of cardboard between lever and housing when removing and installing brake assembly which i didnt do.I sheared off the head of the switch.I ended up screwing a tiny set screw into the center of the switch to take the place of the sheared off part of the switch.A little unconventional but its worked for a couple years.Replacing the entire switch looks like a pain.

 

I’ve disconnected the rear brake light switch and operated the plunger for the front brake switch by hand with the lever off and the light still stays on as soon as the relay makes. Then I hooked the rear brake switch back up and held the front plunger in by hand and pressed the rear brake and the light stays on. Maybe I’m wrong, but I think that proves that both switches are good.

I can hear the relay click once I press the brake. It is possible that the relay is bad? It will engage but not disengage when the brakes are released.

 

Yes they can go bad. Rare they stick "on" but very possible. They're nothing special and don't cost much. Pick one up at any parts store...

 

To understand a relay, you have a coil side and the contractor sides.

So contactors 85 and 86 are your coil terminals. When the brake plunger/pressure sensor are activated, allows continunity across them, which sends power to the coils side of the relay to fire it contractor lever.

So since we don't use the normal closed contractor, but the normally open contractors of 30 to 87A to turn the rear light bulb on, the quick way to check the relay, is to pull it then put a meter on the relay connector pins 85 and 86. When either of the brake lever/pedal sensor are used, should have 12 volts across these pins, and when you let off on the lever/pedal, should lose the 12 volts across these pins. If this is the case, then problem is in the relay with either broken lever spring, or burnt contact pads that are casing lever binding to not allow the lever to release when the coil is de-energized.

If when you let off the lever/pedal, you don't lose the 12 volts across pin 85 and 86, then the problem is back in the lever/pressure switch/there wiring isntead.

Simply pressure switch, and in the case of the front switch, wired through what would be a normal closed circuit that lever pressure with the lever not touched (pushing the plunger inward), will keep the continuity through the switch disconnected,

Note, rear brake pressure switch is wired backwards, hence using it normal open side for wiring, and when it sees pressure from the brake fluid pressure to push it's plunger outwards, makes continuity through the switch instead.

So to check the brake and pedal sensors, just use a meter across the wires with the meter set to ohms, and with the lever out, the brake pedal not touched, should have no no continuity across the wires. Pedal pressed, lever pulled, meter should show a resistance reading, and releasing the pedal/lever, meter should back to showing no continuity through the wires.

 

I appreciate the detailed response. It may be a day or two before I’m able to work on it again. But I’ll report back with what I find.

 

Depending on what part breaks, you can get away with taking the switch apart and just replacing the "guts" of the switch with the guts from a new replacement switch. It will save you the hassle of chasing the wire back to the first factory connection point at either inside the headlight or in the frame (location of connector depends on model). Was lucky enough to get away with that one a couple of times.

 

I unplugged the connector from the relay and now the brake light works as it should…makes me wonder if someone changed some wiring on the bike somewhere