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Tail light doesn't work, brake light does

13K views 10 replies 5 participants last post by  deadbroke 
#1 ·
Hello all,

I've spent the better part of the day trying to install my new Maund Lucas tail light. The LP marker lights are working properly (finally). The brake light is working, but the tail light will not come on. Here is what I have:
  • Maund Lucas tail light
  • Lockhart Philips Marker lights (extra wire for running lights, I'm not connecting it and it's been sealed off)
  • NB rear tail/signal light harness

The tail light has a black and red wire. Red wire of the tail light goes to the red wire of the harness and the black wire to the blue wire of the NB harness. I attached the ground of the harness to the battery while testing. I keep blowing the 5 amp fuses for the tail light and instrument lights. For ****s and giggles I replaced both 5 amp fuses with 10 and the instrument cluster fuse still blew. Even if that had worked I couldn't leave them in there. I'm thinking a bad ground,but I'll be damned if I can figure out where. Shouldn't wiring it to the battery be the best ground you can have, or is that a no, no for lights?

I'm at a loss. Can anyone help?
 
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#3 ·
Trace the wires carefully looking for a pinched wire somewhere. Most shorts are caused by pinching a wire and causing the insulation to break and allows the wire to touch ground. Also piercing wires runs a close second to pinching them. Ever seen a car with a dim headlight on one side? That's what a bad ground will do.
 
#5 ·
I checked again last night and couldn't find a pinched or exposed wire. As well this started happening while all the wires were stretched out & I was figuring out the connections.

Not a bad bulb as I've tried two and a bad bulb shouldn't keep blowing the fuses.

This has really got me bummed out as I want to use this new tail light assembly but I'm considering replacing the stock. :(
 
#6 ·
Is it possible that something is wired wrong? That would be the only other thing I could think of. Something is allowing current to flow directly to ground BEFORE the load- which is the bulb. A short to ground after the load would just be fine as the circuit must return to ground at some point. Hope you find the issue. Shorts can be tough to locate sometimes but are relatively straightforward as far as the technical aspect goes.
 
#7 ·
Well there are only 3 wires. One is a ground with a connector on it to be grounded to the frame or some such thing (I chose the battery for testing) and two other wires going into the tail light. Get those two wrong and it just doesn't work.

Very confused and disappointed with this whole thing. :confused:

Thanks for your feedback Fordtech.
 
#10 ·
Ended up putting the original harness and OEM stop light back in place. I hate to do it, but I just may take the bike and light in to my mechanic to have it done. Let him have the headache of trying to find an electrical fault!

Thanks everyone for offering your advice

Steven
 
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