DRC taillight-hydraulic switch hookup.

I can't remember the wiring connections for hooking up the hydraulic brake sensor switch (two wires) to the DRC stop/tail light (3 wires). Can someone post a quick drawing or description? 

Found it. 


CRFX Wiring.jpg

Just a quick heads up,

don't point a pressure washer too close to your DRC brake light,

especially from underneath while cleaning out the rear fender.



Seeing signs of water droplets inside, mine developed internal short circuits during this past season,

some of the higher intensity 'brake' LEDs flicker / light up by themselves when the regular tail light LED are on.

Edited by mlatour

I wired it up and got nothing!!! No lights at all.  What's going on?


Edited by mikesbaron

Before wiring it up to the bike's harness,

did you test the light (both intensities) before hand by touching the leads on a battery?


Also, if you've inverted the ground and positive leads,

unlike a regular bulb an LED won't function.

Edited by mlatour

I tested it after I didn't get any lights hooked up to the bike with a good battery and nothing! I'm assuming I'm testing correct.... Black to negative post and either red or yellow up positive should yield some sort of light, no?

Yes black to negative and red/yellow to positive should light up.

Yes defective light! Bummer as this is the second one I purchased. First one was broken when received.

I have had problems with stop/tail combo lights also. Now use the stock mud guard light as a stop light and a small red trailer LED as the taillight on the license plate bracket

I still haven't been able to get these DRC led taillight/stoplight set up to work properly. I got a working one sent to me after the first one was bad and I can get the taillight and stoplight to work but the light stays on constantly, even after I shut the bike off. 


1. Where should I be grounding the black wire from the taillight? The only way I can get my taillight/stoplight to work is if I ground it to the subframe or battery. The oem light plugged into a gray female bullet connector and a black bullet connector. Neither of the leftover female bullet connectors from the oem light are grounds, or at least they dont' seem to be. I determined that one of the two plugs, the black plug has constant 12V on it. It never turns off! And thus, my taillight/stoplight never turns off if I have my ground going to the battery and the yellow (taillight/brake light) and black (banjo switch) plugged into the black plug.


What am I doing wrong? It seeems there has to be a way to where one of the two oem female plugs supplies power only when bike is running, no? 


Going by the CRF250X wiring diagram, it's taillight is powered by green grey and black wires.


The black isn't the ground but the positive lead and,

may have constant voltage on it even when the engine isn't running.


The green gray is the ground but, not directly grounded to the chassis but rather through

the Ignition Control Module which no doubt switches it on/off if the engine is running.


By memory, TT forum member CarmanCRF had mentioned to be careful not

to disconnect the taillight while the engine was running as there is risk of damage to the ICM.


The brake light circuit wiring diagram you posted earlier is the correct way to wire things,

you just have to determine which of the original light's wiring is the ground and positive lead. 

Edited by mlatour

Are you saying I need to ground to the green wire out of the ignition module?

Sorry for the typo, I've edited my earlier message to grey (not green)

from you previous post :

10 hours ago, mikesbaron said:

The oem light plugged into a gray female bullet connector and a black bullet connector. Neither of the leftover female bullet connectors from the oem light are grounds, or at least they dont' seem to be. I determined that one of the two plugs, the black plug has constant 12V on it.


From what I can make out of the 250X wiring diagram, 


-the black wire is positive lead and under constant power

-the gray is the ground and is switched on by the ICM only when the engine is running.


If you've grounded the DRC taillight to the chassis, the tail light will always be on.


Ideally you should find a wiring diagram specific to the 450X but it's likely very similar to the 250X.

Edited by mlatour

I only grounded to the subframe to make sure everything was working correctly. When I ground to the gray harness wire the running light will not work whether the bike is running or not. That's what is stumping me. 

The only mods I have on the bike are pink wire cut, heated grips with leads straight to the battery.

Edited by mikesbaron

Careful with tapping into the headlight wires for 12V power, the headlight circuit is actually AC power.

Measure the voltage at idle and again while revving the engine, I've never done it but I'd bet you get a surprise.

So I confirm that my gray ground wire is not becoming a ground when the bike is running. Any ideas on where I should tap into to make the ground  actually work, perhaps with a new grounding wire that has an on-off with the bike running?

Again from the 250X wiring diagram, the grey wire appears to be the only ground which is switched on/off by the ICM.

All other grounds are directly on the chassis. (either a solid green wire or with green + other color).


Perhaps a consideration but myself have chosen to by-pass all aftermarket accessories (DRC tail/brake light, e-fan)

from the bike's original wiring harness to prevent damage to the ICM in the event of a short circuit.


Running a fused link off the battery, thru a small toggle switch, which then feed the fan and tail light circuits.

In this fashion the ICM controlled on/off ground isn't required for the tail light.


Edited by mlatour

What what do you think of this? I round the tail light to the battery or frame. And then I find a hot lead that only his hot when the bike is running? For example, the headlight Hotwire? Do you think that will work? Or is there another wire closer to the battery or rear of the bike that I can tap into that is only on hot when bike running?

As mentioned earlier, the headlight circuit is in AC current.


From I can make of the wiring diagram,

apart from the starter (goes thru a relay) and headlight (fed from the magneto)

everything else (control module, taillight) seems to all pass thru the 15A main fuse meaning is constantly 'on',

reason why it's important to disconnect the battery or pull the fuse whenever working on the bike's electricals.

Edited by mlatour

Is headlight ground a constant ground? If it's not constant then I could ground taillight to there? Then it will only be grounded when headlight is on.



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