Front Brake Light Switch Issue's

[Guest]

So on my 1979 GS750 I have an aftermarket LED strip for my tailight. My issue is that when I activate my front brake lever (I have no rear brake light switch on this bike) the brake light doesnt come on. The running tailights do work. I have working left and right turn signals. When I take the brake light wire from the LED bar and feed it directly to the battery, the brake light turns on. I Ohm'd out my front brake switch and that appears to be working correctly (when I press the switch the tone goes from on to off on my voltmeter.) I checked my orange and green wire behind the headlight with the ignition turned on and i get -12V DC which I think is good since there is power there. I Ohm'd out from the white wire from the front brake light switch all the way to the white wire near the tail section where my brake light is and I get a tone. I checked the fuses and they are all good. I checked continuity from the orange and green to my turn signal relay and I have continuity there. In other words I'm stumped. I think I went thru everything but I know I'm missing something somewhere. I bought this bike used with the LED tailight already there so I'm not sure if it ever did work. But all my findings say that it should...but it dont....any advice? I'm more than happy to clarify or provide pics.

[gsrick]

Is the foot pedal switch working?

[jabcb]

I use an old battery for testing when we do cafe builds. Have noticed that when the battery is a little too flat some of the LEDs don’t light up.


Check the voltage at the brake light wires with the taillight installed & the front brake on. You may have a problem connection some place that drops the voltage down to where the light doesn’t come on.

[Gorminrider]

1979 GS750 ... My issue is that when I activate my front brake lever (I have no rear brake light switch on this bike) the brake light doesnt come on. The running tailights do work....

Do the obvious first. Brake light switches are a very common problem.
(turn signals are irrelevant but given the taillights and brakelights use the same path to ground (negative) I'll assume for now the groundpath is ok...

Follow the wire from your brake switch along the handle bar and to where there is a connection you can pull apart....disconnect them.. Usually these are in the headlight....two "bullet" connectors. I think the connection is orange and white wires from the switch to orange/green stripe and white wires of the electrical system...

Undo these connectors. Get a piece of wire and connect the orange/green stripe and white ends.
Turn your key to ON and your brake light should turn on.
If it does. you need a new switch or to disassemble and fix the switch.

[bwringer]

Polarity matters with LEDs (they're still diodes after all; they just emit light as a useful byproduct...); make sure the negatives and positives are correct.

And yes, GS front brake switches are a terrible, problematic design. You may need to clean or replace.

[602busa]

Is the foot pedal switch working?

The foot brake pedal doesn't have a switch wired to the brake light. Only the front.

[602busa]

I use an old battery for testing when we do cafe builds. Have noticed that when the battery is a little too flat some of the LEDs don’t light up.


Check the voltage at the brake light wires with the taillight installed & the front brake on. You may have a problem connection some place that drops the voltage down to where the light doesn’t come on.

I've done this. I get -12v DC at the brake light switch.

[LAB3]

About the only thing I hadn't seen mentioned was a ground or negative wire.

[Redman]

602busa,a couple points to clairfy:

.- you say led taillight. Then say tailight works but brake light does not.is the brake light part of the led bar that you added? Or is brake light still the original brake light?if the brake light is same unit as the led tail light then , review what color of its wire is suppose to be the common (ground, negitive), which is the taillight and which is brake.

.-you say measured -12vdc at the brake switch?i don’t think you meant negitive 12. Volts, just that had meter leads backwards.did you mean going to the brake switch all the time? Or did you mean after the brake switch only when pull lever in?

.- fairly stock wiring harness? So we can talk in terms of stock wire colors?

[602busa]

602busa,a couple points to clairfy:

.- you say led taillight. Then say tailight works but brake light does not.is the brake light part of the led bar that you added? Or is brake light still the original brake light?if the brake light is same unit as the led tail light then , review what color of its wire is suppose to be the common (ground, negitive), which is the taillight and which is brake.

.-you say measured -12vdc at the brake switch?i don’t think you meant negitive 12. Volts, just that had meter leads backwards.did you mean going to the brake switch all the time? Or did you mean after the brake switch only when pull lever in?

.- fairly stock wiring harness? So we can talk in terms of stock wire colors?

the taillight is one complete LED bar. The OEM tailight is not part of the picture. I am getting 12v to the lead wire for the brake switch to the tailight. Again, I can take the brake light lead wire from the tailight and jumper directly to the positive side of the battery and the brake light comes on. Wiring harness is stock minus this tailight.

[602busa]

Undo these connectors. Get a piece of wire and connect the orange/green stripe and white ends.
Turn your key to ON and your brake light should turn on.
If it does. you need a new switch or to disassemble and fix the switch.

Tried this. I still get no brake light. I'm only getting a brake light when I jump directly from the brake light lead wire to the positive battery terminal.

[602busa]

I could be wrong but I'm starting to think the issue my be with the flasher relay. Thats the only thing between the switch and the brake light wire thats connecting the system together.

[Steve]

It has been mentioned, but I'll repeat it: THE FLASHER RELAY HAS NOTHING TO DO WITH THE BRAKE LIGHT.

Now let's get to basics and start over. You keep mentioning that you get -12 volts. Either put the meter leads in the correct places or toss the meter and use something less confusing - a test light. The BLACK meter lead should be connected to the NEGATIVE terminal on the battery. I should not have to mention it, but I have seen it done - make sure the black lead is in the black jack on the meter.

With the ignition key turned ON you should see voltage on one side of the brake switch. It will be easiest to check at the connections inside the headlight bucket. The orange/green wire should be the hot one. When you pull the brake lever, you should also see power on the white wire. If you don't, clean or replace the switch until you do.

One other thing to check, it involves the tail light itself. Are there three wires? That will help determine whether it, in fact, has tail/brake functionality. If there are only two wires, stop now, get a proper light. No, it doesn't have to be stock, but it should at least have dual intensity.

If the brake light actually powers the white wire, move your meter or test light to the back of the bike to see if the white wire is powered there, too. If it is, then you have a problem with your light strip. If there is no power, trace the wire, as there are a couple of connectors between the headlight bucket and the tail light area.

.

[gsrick]

I'm guessing this is what he has.

QUICK OVERVIEW

12 Volt Super Bright 5050 LED Chips
High quality plastic construction
Lightweight and waterproof
Includes 3M Adhesive Strip
Red Brake and Running Lights
Amber Turn Signal Indicators
Length: 8"
Width: 0.5"
Wire Length: 38.25"


Wiring Guide:
Black = Ground
White = Running
Red = Brake
Green = Signal
Yellow = Signal

[Redman]

....the taillight is one complete LED bar............
.................................................W iring harness is stock minus this tailight. ... ... ......

1) Find the White wire connector near the front brake switch, in the headlight bucket probably.
You have 12v on the White wire from the brake switch when pull the lever?
and about no voltage when dont pull the lever?.
The White wire.
THe White wire FROM the switch, plugged into a white wire of the bike, probably in headlight shell.
(Not the Orange/Green (or Orange) wire TO the switch, that should have power all the time the key is on.)

2) You have 12v on the white wire of the bike near the brake light when pull the lever?

3) The light bar has 3 wires?

4) what color wire on your LED light bar is suppose to be the brake light?
and you have that connected to the white wire of the bike?

5) what color wire of your LED light bar is suppose to be the common/ground/negitive?
and that is connected to the bikes black/white wire or grounded somehow?

6) what color wire of the light bar is suppose to be the tail light?
and you have that connected to the bikes brown wire?

Lets answer the questions 1 thru 6.
Then proceed.


If 1=yes but 2=no,
well then you are loosing it along that white wire somewhere between the front brake area and the rear of the bike.

7) Other note, other thought. ....
You say there is no switch on the rear brake pedal.
Did you take out the wiring to that switch? Didnt pull those wires out of the wiring harness did you?