Tail Light Surge

[wbabik]

I'm not sure when this began occuring, but since I tipped her over towards the end of last year, I have made many modifications and the result is a little bit of a problem.

Background and mods: 1996 VFR750F - tipped over.

Modifications: fiberglass undertail fender, corbin, homemade license plate bracket,

Relevant modifications: heated grips, fuse box on relay tied into the license plate wiring, LED from www.superbrightleds.com for gauge cluster, volt meter tied to the fuse box.

Problem: When the brake is applied, the left taillight bulb fades out and the right taillight bulb gets brighter as it should.

1. If the bulbs are switched the problem stays with the bulb fixture.

2. If the green wires are switched from one assembly to the other the problem goes with it (ie: to the other bulb).

I can't seem to find the wiring layout exactly with the microfiche. Does anyone have any input here? What do I try next?

wiring harness link:

http://www.ronayers.com/fiche/200_0295/wir...rness_94-97.bmp

taillight link:

http://www.ronayers.com/fiche/200_0295/tai...t/taillight.bmp

I've searched and read countless electrical posts and I can't seem find anything that will help me out. I've also tried electronic cleaner and checked the connections in the subharness connection to the main electrical harness as well as sprayed the bulb connectors. nothing changes the symptons.

thanks for your help. hopefully I can get this resolved soon. I need to get out on 2 wheels again.

Will

[V4 Rosso]

Did you modify #5 in the second pic in any way? Maybe switched the common ground terminal in the connector, effectively putting the tail & brake light (of the duplo bulb) in series when the brake is applied?

[wbabik]

That is what is strange. I didn't modify the #5 on the second picture at all. Nor does it appear to mate up with any other mods. unless the gauge cluster somehow interferes here? not really sure on that front.

I thought the load would have changed if they were in series, thus causing one to dim, with that thought in mind, would they both dim in series? it seems one works fine and the other doesn't. I guess I have to tear off the bodywork and begin tracing wires. maybe the ground for the defective side is faulty/dirty/??

I appreciate the comments. anyone else have anything here? I need ideas on this one.

[Tightwad]

try changing the green wire at the plug, to see if the problem is in the #5 harness or the main harness assembly. When you say the taillight fades, do you mean the taillight filiment goes out, but the brake light one comes on? Or both go out, while both of the right side are on?

[wbabik]

I'll try that tonight. changing it at the plug on the sub harness. then it will isolate the main harness from the subharness.

Bulb #1: taillight running light filament goes out and the brake light doesn't come on. ie: no light from bulb at all.

Bulb #2: brake light comes on. ie: both filaments are lit. or at least the bright one is. I would have to confirm that the running light stays lit when the brake filament comes on.

thanks guys. this is helping get me focused on the troubleshooting process here.

[V4 Rosso]

I don't mean the two bulbs are in series but the two filaments of a single (fading) bulb. A 4th gen does have two combined (duplo) tail- brakelight bulbs, don't it?

Both filaments in a single bulb have a common ground, but if you switch the terminals of the connector so that the ground terminal is now where normally one of both positives is located, it means that for one of the filemanets the current is just reversed, no problem. But for the other it means the current has to pass through both filaments so less current will flow. Likely there will not flow any current through one of the filaments as there is no voltage drop over the (brake) filament. It may look however that it fades, but that may just be your eyes playing tricks on you as the other brakelight lights up and the size of your pupils decrease. You can check this by detaching the connector from the non fading bulb and watch closely as you apply the brake.

Edit: I did not see your previous post before I posted my reply. Now that you mention that both filaments go out, that could indicate that that bulb has no direct ground but the running light finds its ground through the brake light filaments of both bulbs. If that's the case, you should be able to notice that the fading running light is slightly dimm compared to the other running light (about a third less current goes through the three filaments in series) while not applying the brake.

[wbabik]

Problem solved!!!!!!!!!!!!!!!!!

Wooohoooo.....another electrical gremlin solved.

Ready for inspection and back on the road.

Solution:

I removed the subharness that connects the main wiring electrical harness to the two tail bulbs. Then I removed the green wire that goes from the same connection at the wiring harness end, to the two bulbs. I took two pieces of 12 gage stranded copper wire and soldered them to the exposed piece of wire on the connector side and soldered the other ends directly to the bulb fixtures.

Violla. problem solved. no more dimming of the one and a better connection in general. should not be prone to any vibrational issues. etc.

Those crimps are just evil gremlins waiting to happen.

Thanks V4 Rosso and Tightwad for your insight. Got me motivated and thinking on the correct troubleshooting track to get this thing back into business.

AWESOME!!!

Thanks

Will

[Tightwad]

Where is this connector located? I am still looking for a way to tap into a switched power, without doing any cutting.