Rear brake not activating brake light

[1stFz07]

Hey guys, I have driven TT rearsets installed on my 2016 Fz07. I have the pressure switch installed as well. So I tried to play around with the rear brake and accidentally loosened the master cylinder bolt to see if I can make the brake lever tighter, and I noticed that the brake light stopped working (only for the rear brake). 

I noticed this after I went to wash my bike at a car wash (DIY). Now Idk if it’s the water that might’ve gotten into the relay or may be I need to get a new pressure switch or I need to bleed my brakes and try it again, OR a pinched wire? Lol I’m so confused. 
 

pls help. 

Edited April 22, 2021 by 1stFz07

[Pittsburgh pilot]

Does the hand brake activate the tail light?

[DewMan]

9 hours ago, Pittsburgh pilot said:

Does the hand brake activate the tail light?

If the bike is in proper working order, Yes it should.

[Pittsburgh pilot]

The switch may  simply need adjusted. The foot brake lever actuates the rear brake light through a spring attached to a switch. That switch can be adjusted up or down affecting when or if the tail light comes on. If you remove the right side frame guard you will see and have access to the switch.

[D.A.]

14 hours ago, Pittsburgh pilot said:

...The foot brake lever actuates the rear brake light through a spring attached to a switch...

That’s the way it works on a stock bike but not in this situation because the original poster no longer uses his spring-activated OEM brake light switch. He removed it when he installed race-oriented rear-sets designed for use on tracks where bikes aren’t allowed to have any functioning lights.

To use these pegs on his street bike, he added a $20 device that attaches directly to the rear master cylinder. When the pedal is pressed it detects the increase in brake fluid pressure and triggers the light.

It’s basically a banjo bolt with a built-in contact switch. It has a wire that connects to the bike’s harness where the spring-activated OEM light switch normally plugs in. To install, you remove the OEM banjo bolt from the top of the rear master cylinder and insert the pressure switch in its place. 

It’s a super-simple device that works but can’t be adjusted.

Edited May 7, 2021 by D.A.

[D.A.]

16 hours ago, Pittsburgh pilot said:

Does the hand brake activate the tail light?

@1stFz07: As Pittsburg pilot suggests, verifying the hand lever activates the brake light is the first step in troubleshooting the issue. 

If that checks out I’d use a meter to verify the pressure switch and its wires still work. 

Then you should verify that your pressure switch’s connections and solders (if you made any) are intact by disconnecting everything, cleaning with contact cleaner and reconnecting.

Next option is to temporarily reconnect the OEM spring-activated switch and trigger it by hand to verify there’s not a wiring problem with the harness.

Air in your rear brake line is the most likely culprit but I would try the other options first since unnecessarily bleeding the brake wastes fluid, is messier and would be more time-consuming. At least it would be for me!

If all of the above checks out you may need a different brand of pressure switch because some of them are reportedly more sensitive than others and your recent master cylinder adjustments may have pushed you over the threshold of where your current switch functions correctly. 

Before doing that, though, you might try readjusting your brake pedal back to the height it was at before you started messing with it. 

Edited May 6, 2021 by D.A.

[ElGonzales]

I once made a online simulation of our tail light some days ago in EveryCircuit to play around.

The function with two brake light switches (you can press them in the simulation with the left mouse button and see the reaction) is working like in reality. But there are only two LEDs and the displayed values aren't correct.   However, the functionality corresponds to the wiring diagram:

https://everycircuit.com/circuit/4610569985064960