Every fix is just a band-aid

[JapanStan]

I have now owned my 2004 12R for a full year. The two previous owners have insured that I became at one with my profanity. Electrical issues everywhere, front to rear. Right now the current issue goes like this: I have (for the 5th time) *fixed* my tail light. The light will intermittently go out. The brake light will still function so I don't worry too much when stopped at a light. But the running light is very important for visibility at night. So what do I do? I take the assembly off, check the wires and connections, check the bulb, test everything, and I get a 50/50 chance it works.

At this point I assumed my rear light assembly was bonked, but I had a spare laying around from another tail section I purchased earlier. Still the same issues. So off goes the rear body work to chase some wires. Everything looks kosher, and I cannot figure out where my issue is. Everything tells me it has to be rear assembly, maybe something as simple as the connections touching the bulb, but nothing I do fixes the issue permanently. OK.. Right now I have the brake light and running light working. I will go for a ride later to see if it works, or fails again.

Another interesting electrical issue that I have bandaged, though not solved goes a little like this. Low beam headlight assembly keeps melting. I mean the thing goes full on nuclear. So I check the power of the bulbs, everything checks out. I make sure I am using the correct 55w H3 bulb. Have some friends and my father check everything with me to make sure I am not going insane. After 10-20 hours of riding the assembly is fried. I go through like 3 of these things, and they aren't cheap. WHY IS THE LOW BEAM SO HOT? I run during the day with the high beam always on, and it has the same bulb as the low, yet the high is just fine. So I wise up and decide to get a lower wattage bulb for the low beam. I go with a 35w bulb. But just for giggles, I grab my infrared thermometer and read the temps. The 55w high beam is running at 114 degrees. The 35w low beam is at staggering 145 degrees. Both have the correct power running to them. I don't even want to know how hot the 55w bulb was burning.

I now have a LED bulb in the low assembly, which is crap at night. I cannot scratch my head enough over these issues. I think I need an entire new wiring harness.
Great bike, I love my Buell. But good lord did I get a difficult one.

[cjanderson_90]

Can you check that the battery is holding 14.2 V at 3000 rpms? Id check that first. If its more, you have a VR problem. If its less, you have a VR problem. Im leaning towards a VR problem.

[mrlogix]

check the ground for the headlight issue

[rchuff]

Could it be the banjo fitting on rear brake be going bad ? Have you checked that?

[Custom_buell]

Sounds like a possible ground issue with both your headlights and tail light

[Chicknstripn]

There's a 30 amp fuse down near the bottom left section of your tail section. I believe you'll find it near the active exhaust servo plug and the rear tail light sub harness. Not sure if that could be your issue but I would check that.

[Rays]

There is a chance the ignition switch being at least part of the problem. I had a mysterious intermittent tail light on my '06 Uly that had me puzzled for a while.
There are two separate contacts in the ignition switch and when the switch is moved to the 'On' position pin 1 is connected to pin 3 and pin 2 is connected to pin 4 internally in the switch.
Power (+12v) is connected to pins 1 & 4 of the ignition switch. By the 'On' connections described above there are effectively 2 power circuits.
The connections to pin 3 include all of the main operational items but the connections to pin 2 only include the items that are on when the switch is in the 'Park' position.
That includes the taillight and Euro light and the blinkers. If you have a dirty connection for this in the ignition switch a bit of jiggling around should restore the tail light temporarily - you can see how this can really lead you astray given every time you switch the bike on and off might 'fix' things for a while.
If you lose the tail light again just try the blinkers to see if they are still working. If so, then move on but if they are also dead then the ignition switch theory is looking stronger. You can remove the electrical part of the ignition switch and clean the contacts (fiddly but definitely possible). You need a security Torx T45 to remove the ignition switch body.