Rear Brake Light and Front Brake "Switch"- Look Ma, no lights!

[dbvolfan]

Looking for some advice here as I thought I had it nailed down but the 'fix' didn't work.

The rear brake light will not come on when the front brake lever is activated. I first cleaned and then finally replaced the front brake switch assembly (the small component just under the front brake lever). Still not working. I figured it was that switch for sure as this bike rides a lot in the rain and snow and 7 yrs of grime could wear that contact out.

The rear lights do work and the brake lights work fine when the rear brakes are applied.

Any advice on what to check next? I'll try to dig into the SVC manual a bit more tonight as well.

 

[dbvolfan]

Well, I was able to establish that the new switch works as well as continuity in the first harness that leads from the handlebars to just inside the engine compartment where it feeds into the big one (both green/yellow and brown wires tested fine)

Also established continuity between the brown wire that comes out of the rear brake switch and goes to the rear lights. Also get continuity on the brown wire between the big harness and the rear lights.

I do not however get any continuity between the green/yellow wire at the beginning of the large harness at the front of the tank to the relay under the seat. Dont yet know if that is good or bad as I need to study these electrical diagrams some more. I have never messed with electrical so this is all virgin territory. I dont see any visible damage, crimps or cuts that might lead me to believe it's that but I cant rule it out as there are so many wires!

I do know that the old switch got VERY hot when put in and didn't work...so hot you couldn't touch it.

The new switch stays cool but works about 75% of the time. It seems like when I am less likely to get light when it is in the open position for an extended time and then I 'brake".

 

[dsmack]

What other, if any, farkles have been installed on your bike? Any of them tied into the lighting system, such as a "Back Off" brake light flasher module?

Sounds to me like there is an intermittent short somewhere in that circuit that may well have caused high enough resistance to burn out/heat up your original switch.

Take my comments with the proverbial grain of salt though, as trouble shooting electrics is NOT my strong suit!

Good luck with your efforts...

Don

 

[Rogue]

The yellow wire goes from the front switch back and splices to the yellow from the rear brake and straight to the brake bulbs.

It has to be a broken/shorted wire.

 

[dbvolfan]

No mods whatsoever.

Looking at the electrical diagrams I noticed the yellow/green runs into the large harness and eventually splices below the ECU (wrapped in tons of protective tape). The yellow then run to the rear lights, just as you mentioned.

There is continuity along that path.

To recap:

Rear lights work just fine

Real Brake lever activates the rear brake lights

Rear brakes did not light at all with old switch (switch was however extremely hot)

New switch appears to stay cool and work maybe half of the time but still getting no rear brake lights ~50% of the time

No visible damage to the wires. All connections appear to be snug and whole

Continuity at the switch is fine as well as the segments of the harness I have tested so far. I have essentially confirmed there is continuity from front brake switch to rear taillights

Continuity between the rear brake switch and the rear lights is fine as well.

I agree that is sounds as if it is an intermittent short or break. Should I be looking for a consistent 12v power along these tested segments instead of continuity? That might reveal the break.....I tried wiggling some wires while testing for continuity but that didnt yield anything. It was 1 am at that point so maybe I Need to go back and try it again as I was cooked at that point. Or, is there a specific fuse outside the main fuse box that could be a culprit (I dont see one on the electrical drawings but I am no electrical expert)

I appreciate the help....I have this thing torn down for some other work so the timing is right but this is my worst nightmare in terms of repairs as I know nothing about electrical (but am studying it quickly)

 

[dsmack]

No mods whatsoever.

Looking at the electrical diagrams I noticed the yellow/green runs into the large harness and eventually splices below the ECU (wrapped in tons of protective tape). The yellow then run to the rear lights, just as you mentioned.

There is continuity along that path.

To recap:

Rear lights work just fine

Real Brake lever activates the rear brake lights

Rear brakes did not light at all with old switch (switch was however extremely hot)

New switch appears to stay cool and work maybe half of the time but still getting no rear brake lights ~50% of the time

No visible damage to the wires. All connections appear to be snug and whole

Continuity at the switch is fine as well as the segments of the harness I have tested so far. I have essentially confirmed there is continuity from front brake switch to rear taillights

Continuity between the rear brake switch and the rear lights is fine as well.

I agree that is sounds as if it is an intermittent short or break. Should I be looking for a consistent 12v power along these tested segments instead of continuity? That might reveal the break.....I tried wiggling some wires while testing for continuity but that didnt yield anything. It was 1 am at that point so maybe I Need to go back and try it again as I was cooked at that point. Or, is there a specific fuse outside the main fuse box that could be a culprit (I dont see one on the electrical drawings but I am no electrical expert)

I appreciate the help....I have this thing torn down for some other work so the timing is right but this is my worst nightmare in terms of repairs as I know nothing about electrical (but am studying it quickly)

Like the referees like to say in the NFL: "Upon further review...", after re-reading your response above, I'm leaning toward a possibility of a mechanical problem in addition to the original problem of a defective switch that overheated.

I did a Google search on Brake Light Switch problems using a variety of search criteria. One that returned some good info was Brake Light Switch problems site:FJRforum.com

Hidden in the archives of this site are discussions that point to a problem with splooge (a highly technical term) building up in and around the handlebar mounted switch. Also mentioned are a couple of problems where the build-up has actually caused parts of the handbrake/switch assembly to become sticky enough that it either would not activate the lights, or, once activated would not freely release the switch to allow the lights to turn off.

Where you are getting successful activation ~50% of the time now with the new switch, I'm wondering if you've solved the electrical part of the problem, and now only need to ensure that the brake lever, pivots and assorted other parts are properly clean and correctly lubricated?

There was also a somewhat related thread from not too long ago where the OP thought he had a problem with the switch, but eventually found the solution to be re-bleeding the brakes...

I hope you find it is something simple. Trouble shooting intermittent electrical problems can be a real bugger! :dntknw:

Good Luck

Don

 

[dbvolfan]

Thanks for the info!

I'd like to think that I have it fixed as I have not been able to replicate the issue in over 2hrs of testing.

I had continuity along the entire line, from the switch to the tail lights. I wiggled the lines while testing and didnt notice anything there either.

No crud buildup at the bar but nonetheless, I disassembled it and cleaned it up.

I did notice that the harness connection just below the steering head bearings was pretty contaminated. It had some corrosion and copper like patina. I ended up disassembling every harness along the circuit, cleaned them with contact cleaner and reconnected them using some dielectric grease. No issues after doing that.

If I had to guess, I think the harness by the steering head got loose when I had it in the shop last month for some work.

They did a valve check and that little rubber mat tucked in under there is a tight fit. Moving all that AI piping around and stuff, I could see where it might have wiggled loose or something.

So, for now I am keeping my fingers crossed and hoping this gremlin doesnt reappear......thanks for the info however!

 

[3dogs]

If you suspect a short/open in the wrining from the brake sw to the brake lt (may be burried within the wiring harness) you can always run your own wires from the brake sw (or where ever you can get to a known good section of the original wires) to a known good section near the rear brake lt. I worked on cars for years and often times this type of solution was more cost effective than actually finding a bad section of wire hidden in an impossible place to reach (door pillers, roof liners, main engine management wiring harness that 2" thick etc.).