Front Brake Switch

[scouser]

I hope some one can help with this one.
I have an issue with the front brake switch lighting up the rear brake light.
Ihave checked voltage through the wiring harness for the rear brake right up to the 3 wire plug at the lights and everything works fine and the brake light lights up.
I have checked the wiring harness through the front brake switch right up to the 3 wire plug at the lights. I have 12vDc when the brake is applied but from the plug to the bulbs nothing lights up.
doesnt make any sense to me as both brakes have power to the plug but rear works and front wont.

[FJmonkey]

I got two different messages from your post, the front brake switch illuminates the brake when it should not, and the rear does not illuminate when the front brake is applied. If the wiring is good then the switch is likely the problem. Have you put a meter on the switch (continuity check) to make sure it changes states when actuated? Is this a new problem? If so what was done work wise recently (just before the problem started) that might affect wiring?

[scouser]

back brake works
front does not
both have 12vDC going to the 3 wire plug (checked and verfied when lever pulled and peddle presssed) just before bulbs.
front brake swithch checked and works correctly

[rktmanfj]

back brake works
front does not
both have 12vDC going to the 3 wire plug (checked and verfied when lever pulled and peddle presssed) just before bulbs.
front brake swithch checked and works correctly

When I was running the stock m/c, the front brake light switch had to be changed 2 or 3 times... never did figure out why.   

Never a problem with the R1 unit.

[craigo]

Do you have a FJR master cylinder on your bike?

CraigO

[scouser]

cant figure out why I get voltage at the plug before the bulbs when both front and back is applied and only the back lights it up. switch is working if voltage is allowed to pass through when both are applied.

back brake works
front does not
both have 12vDC going to the 3 wire plug (checked and verfied when lever pulled and peddle presssed) just before bulbs.
front brake swithch checked and works correctly

When I was running the stock m/c, the front brake light switch had to be changed 2 or 3 times... never did figure out why.   

Never a problem with the R1 unit.

[scouser]

Bike is all stock.

Do you have a FJR master cylinder on your bike?

CraigO

[Pat Conlon]

Ok, let me try...
You do know that you get 12v power at the rear lamp plugs when you turn your key on...correct?
For the Running lamps.
A second circuit supplies a additional 12v to the lamp plugs when the front/rear brake switches are activated
That's how the light bulbs get brighter...the second filament in the bulb burns when the brakes are applied.
Therefore, don't confuse the 12v readings at the rear lamp plugs, you should get 2 readings, one for the running lights and the second for the stop lamp filaments.

Forget about the rear brake switch ..it's working
Forget about the light bulbs and bulb sockets, they work when the rear brake is applied.
Now...............
With the key on....When you unplug the 2 wires from the front brake master cylinder (m/c) and touch them together
Does the rear brake light come on? (Not the running lights, they should come on when you turn the key)
Yes or No.
If yes, then the problem is with the switch...if no, then the problem is elsewhere.

[yamaha fj rider]

Well stated Pat.

Kurt

[scouser]

Thanks for the reply.

I tested it by checking from putting the tester on the wire in the harness and the other probe to ground. No voltage reading until I pressed the back brake and front brake. Each time I got a good reading of 12vDC.
however only the back works.
I will be checking it over again with the information you have given me.

thanks.

Ok, let me try...
You do know that you get 12v power at the rear lamp plugs when you turn your key on...correct?
For the Running lamps.
A second circuit supplies a additional 12v to the lamp plugs when the front/rear brake switches are activated
That's how the light bulbs get brighter...the second filament in the bulb burns when the brakes are applied.
Therefore, don't confuse the 12v readings at the rear lamp plugs, you should get 2 readings, one for the running lights and the second for the stop lamp filaments.

Forget about the rear brake switch ..it's working
Forget about the light bulbs and bulb sockets, they work when the rear brake is applied.
Now...............
With the key on....When you unplug the 2 wires from the front brake master cylinder (m/c) and touch them together
Does the rear brake light come on? (Not the running lights, they should come on when you turn the key)
Yes or No.
If yes, then the problem is with the switch...if no, then the problem is elsewhere.

[scouser]

Thanks again you are correct.

I just tried it the way you explained and it lights up when touching the wires togther..

I will be taking off the switch and check it out.

Cheers.

Ok, let me try...
You do know that you get 12v power at the rear lamp plugs when you turn your key on...correct?
For the Running lamps.
A second circuit supplies a additional 12v to the lamp plugs when the front/rear brake switches are activated
That's how the light bulbs get brighter...the second filament in the bulb burns when the brakes are applied.
Therefore, don't confuse the 12v readings at the rear lamp plugs, you should get 2 readings, one for the running lights and the second for the stop lamp filaments.

Forget about the rear brake switch ..it's working
Forget about the light bulbs and bulb sockets, they work when the rear brake is applied.
Now...............
With the key on....When you unplug the 2 wires from the front brake master cylinder (m/c) and touch them together
Does the rear brake light come on? (Not the running lights, they should come on when you turn the key)
Yes or No.
If yes, then the problem is with the switch...if no, then the problem is elsewhere.

[Pat Conlon]

Ok, that's common, I've been through a couple of brake light switches myself...they do wear out.

Kudos for sticking with it... Cheers.

[SlowOldGuy]

I've replaced the front brake light switch on my '85 at least 3 times. 

Try prying the switch open and cleaning the contacts.  That's worked for me in the past.

DavidR.

[Derek Young]

Ok, let me try...
You do know that you get 12v power at the rear lamp plugs when you turn your key on...correct?
For the Running lamps.
A second circuit supplies a additional 12v to the lamp plugs when the front/rear brake switches are activated
That's how the light bulbs get brighter...the second filament in the bulb burns when the brakes are applied.
Therefore, don't confuse the 12v readings at the rear lamp plugs, you should get 2 readings, one for the running lights and the second for the stop lamp filaments.

Forget about the rear brake switch ..it's working
Forget about the light bulbs and bulb sockets, they work when the rear brake is applied.
Now...............
With the key on....When you unplug the 2 wires from the front brake master cylinder (m/c) and touch them together
Does the rear brake light come on? (Not the running lights, they should come on when you turn the key)
Yes or No.
If yes, then the problem is with the switch...if no, then the problem is elsewhere.

Very well written Pat.  I was having a hard time deciphering the original post, it was quite confusing.  You simplified it well and hopefully scouser can get it sorted out.  You have a way of explaining things that make it easy to understand.  Your posts have been very helpful to me in the past.  Keep up the good work.

Thanks
Derek

[Pat Conlon]

Thanks Derek. I am looking forward to seeing you and your lovely Donna at the WCR!  Cheers!  Pat