Rear brake light plug question

This past weekend a buddy and I were riding and he brought to my attention that my rear brake light seems as if it was always on. I looked at it and it does look to be very bright with the brakes depressed. When I engage the braked, the is a noticeable difference in it being a tad brighter but not as much as his and definitively something that a vehicle behind me would have trouble noticing. 

That said, last night I took a look at the plug (bike harness) and both pins are showing 12V constant when testing them individually.

Should they both always have 12 volts?

Shouldn't only 1 have 12v with brakes depressed? And the other no current…

Which wire is running light and which one is brake? 

At this point I am thinking there has to be either an issue with the wiring or an issue with the brake switch. Any ideas on how to troubleshoot and in what order?

Check that the bulb is installed correctly. It is possible to force them in incorrectly.

1 minute ago, Padilen said:

Check that the bulb is installed correctly. It is possible to force them in incorrectly.

My bad, I forgot to mention that I do not have the original tail light assembly installed. I bought an LED light... Can't remember the brand. 

looks just like the below and came already with the harness. 

 

Smoke-LED-Tail-Brake-Light-For-Suzuki-AT

Normal for leds, they share a common voltage source, and will pick up any slight remnants in the line. You could install a diode if wanted. Will prevent feedback. My rear red light is switched on to the ign. It gets brighter when the brake is applied. I also have my turn signals in the same housing

 

My light looks just like that, but on the very edges has yellow leds for turn signals. These lights weren't designed to be visible, lol. They were designed to make the the legal requirement.

 

 

1 hour ago, drtman said:

My bad, I forgot to mention that I do not have the original tail light assembly installed. I bought an LED light... Can't remember the brand. 

looks just like the below and came already with the harness. 

I have this same tail light. I can't remember what colors the 3 cables are, but it's very simple. Get some bullet connectors and connect them to the wire harness in all possible combinations, and press the brake lever. IIRC, one will work, one will be the opposite (gets dimmer when brakes pressed), one will stay always on. 

Same concept, just have wrong wire connected. Not sure if all that type LED lights are made the same but I'll run out and get what I have as wire colors for what light.

 

I have

Black-ground

Green- tail light

Red- brake.

 

Had more time to play with them this evening. No matter what wire combination i use, it keeps lighting up at same brightness for both running light and brake light.

Had more time to play with them this evening. No matter what wire combination i use, it keeps lighting up at same brightness for both running light and brake light.
Try a different light.if you still have the problem it could be bad ground. Or somewhere the wires are in contact with each other.

No go.

Just took the entire light out and tested the cables directly to the battery to eliminate a possible brake switch problem and it is definitively an issue with the light.

All possible combinations = same bright light output.

18 minutes ago, drtman said:

No go.

Just took the entire light out and tested the cables directly to the battery to eliminate a possible brake switch problem and it is definitively an issue with the light.

All possible combinations = same bright light output.

It sounds like a poorly made version.  Usually there is a couple of diodes to prevent back feed and a couple of resistors.  One resistor provides voltage drop /current limiting for the taillight circuit and the other (usually of lesser value resistance) current limiting / volts drop to the brake circuit.  You could always graft in another resistor to the tail light circuit to drop the brightness a little.

9 hours ago, roleyrev said:

It sounds like a poorly made version.  Usually there is a couple of diodes to prevent back feed and a couple of resistors.  One resistor provides voltage drop /current limiting for the taillight circuit and the other (usually of lesser value resistance) current limiting / volts drop to the brake circuit.  You could always graft in another resistor to the tail light circuit to drop the brightness a little.

Agree. I bought it used on Eba.... from a part out DRZ and thought it was a good deal at $5.00 and came with harness and bracket.... Oh well, at least I now have the bracket and harness and just need to either add a resistor or buy a better light. 

Agree. I bought it used on Eba.... from a part out DRZ and thought it was a good deal at $5.00 and came with harness and bracket.... Oh well, at least I now have the bracket and harness and just need to either add a resistor or buy a better light. 
5$ is about the price of the light ! Got mine on eBay from China, 2-3 years ago. But I do have a spare, because I don't trust a 5$ light.

I got the DRC tail tidy kit (for which I paid good money about $100NZ). The quality is excellent.  I decided that I didn't want serrate indicators so printed a bracket and incorporated an amber row of LEDs in the DRC light.  Its been super reliable so far.  Its even done a few river crossings  and mud bogs in adventure mode.

 

DRC_Wroking.jpg

DRC_Left.jpg

DRC_Right.jpg

I have a TST Industries tail light set up. I had the same problem and it turned out that my foot brake switch was engaging the switch. A couple of turns of the screw and it was fixed. Bright light when pressed and running light when not pressed. 

I have a TST Industries tail light set up. I had the same problem and it turned out that my foot brake switch was engaging the switch. A couple of turns of the screw and it was fixed. Bright light when pressed and running light when not pressed. 


Unfortunately for me that was not the case although I was hoping it would.

I took the light and tested the leads individually with a car battery and both leads throw the same brightness.

sounds like a defective light then.... you can get a new light for $15

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