LED tail light stopped working - low voltage?

[phesby]

I've been running a UFO LED tail/brake light on my bike for the last several months. I don't do much riding at night, but on the way home for a local bike night I was alerted that my tail light wasn't working (brake light still worked). I pulled the light and sent it back to Jon at UFO to take a look and he said it bench tested ok, so it appears to be a problem with my bike. The tail light is on it's way back to me, but in the meantime I'm trying to figure out where my issue is...

With the key off the voltage across the battery is 12.65. When I turn the key on it drops to 12.3 or so. At the tail light I'm reading 11.5 volts and am getting a similar reading on the brake light circuit (as mentioned above, the brake light worked fine). It does seem strange that I'm losing about 0.8 volts from the battery back to the tail light. Does anyone know if this is typical and if not where to start troubleshooting?

 

[gamorg02]

the 11.5 v shouldn't keep it from lighting regardless. do u have the stock you could throw in?

 

[ninjaneer]

make sure the yellow or blue wires are connected solidly--i forget which one is the brake and which is the "running". it sounds as if a connection came loose.

do you still have the OEM light? if so, hook it up while you wait for the UFO and see if it behaves properly.
{EDIT: hehehe gamog02 beat me to the punch. if you don't have the taillight, hook a rear turn signal to the yellow and blue and see if you can get it to light up with a brake and ignition switch (Key On)}

 

[phesby]

Thanks, when I get the light back trying to swap the yellow/blue just to see if I can get the tail light to light up is going to be the first thing I try. I didn't do a lot of troubleshooting before I sent it back in as I assumed it had gone bad. My connections were all good and I used a test light to confirm that I had power all the way back to the light.

 

[ninjaneer]

btw where 'bouts in florida dya ride?

 

[phesby]

I'm in Punta Gorda. Not riding anywhere till I get my lights figured out! :ummm:

 

[tugla]

did you try both the foot and hand lever to confirm power at the light? maybe switch in hand lever is stuck or same with the foot one.

 

[phesby]

Both of the brake switches are ok and operate the brake light properly. It's just the tail light that is not working (simpler circuit, so no reason this shouldn't work).

When I get the LED light back and if the tail light works when wired directly to the battery, but not to the tail light wiring, then I'll probably revert back to a tail light with a regular bulb instead of LED...

If anyone has put a volt meter on their tail light wiring by chance let me know what kind of reading you get.

 

[tugla]

ya that does sound weird. whats your voltage with bike running, idle and 3G?

 

[dkw0417]

Unless I missed something(i am reading on my phone), if the LED is working and you circiut wont light it, I doubt it will light a regular bulb

 

[phesby]

Just a follow-up on where I ended up. The previous owner of my bike had replaced the reflector behind the passenger seat with a light. This light and the rear turn signals were all hooked up to the brake light wire (yellow). When I hooked up my LED tail light to just the blue (running light) and black (ground) it worked fine. As soon as I hooked up the brake light wire (yellow) the running light would no longer work. I unhooked the turn signals from the brake light wire and then the LED running light worked, but strangely enough the reflector light lights up as well. I saw another post on this forum where a guy had to put a diode in the brake light circuit as his LED tail light was back-feeding the brake light circuit. I seem to be experiencing the same issue. With the turn signals connected to the brake light the back-feeding issue appeared to cause the amps to drop enough so the LED running light wouldn't work at all.

For the time being I'm using a regular (incandescent) tail light and now the running light works fine and the reflector light only comes on when I hit the brakes. I'll have to look into the diode option when I get more time to mess with this, but just wanted to relay my experience for others with LED tail lights and extra lights hooked up to the brake light circuit.