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13,859 Posts
Discussion Starter · #1 ·
I have wiring questions.

I'm working on lighting on both 2005 EFI LowRider and VrodB. I'm not inclined to use HID.

What is the actual gauge of the stock headlight wiring? I have replaced both stock lights so I know they are the same, I should know gauge by sight but do not.

Anybody know or read anything about relays giving improved light output? The bulbs I'm planning are 70/65W.

I also have Raptor shift lights for both bikes, the Vrod forum has detailed instructions and pix for the light wiring, and they specify the ECM unused output socket #3 as the source of the tach signal needed. I'm comparing the wiring diagrams in both service manuals, they seem to be the same in this regard, actually the LowRider diagrams even more clearly label the ECM pin #3 as tach output, and it is also unused. I'm thinking this is about as good confirmation as it gets, but thought I'd ask if anybody else has done this wiring hookup on a Dyna?

212 Posts
The wiring for the headlights is 18 ga.

If you are planning on adding Relays to power the lights, I think that would be a great Idea. It would theoretically improve your power delivery, but I can't honestly say I've measured the difference. The 65w high beam on my 2003 A draws about 4-5 Watts. It's definately enough to justify its own relay in my opinion.

I can't help with the shift light, as I have not wired one up, YET. :D

13,859 Posts
Discussion Starter · #4 ·
Data for relays from Dan Stern Lighting

Diminished light output from voltage drop

10.5V : 510 lumens
11.0V : 597 lumens
11.5V : 695 lumens
12.0V : 803 lumens
12.5V : 923 lumens
12.8V : 1000 lumens ←Rated output voltage
13.0V : 1054 lumens
13.5V : 1198 lumens
14.0V : 1356 lumens ←Rated life voltage
14.5V : 1528 lumens

Wire gauge / length / load calculator

There isn't much option to give source voltage, 12 volts even is all they offer.

If my math is correct, I calculate my 70W high beam and 2 50W driving lights, at 170 watts,
will pull a theoretical 14 amps

18 gauge
calculating 5 feet 1 way (with the run to and from the switch) and not counting the switch,

the voltage drop is 7.68% .921 V drop for a delivered voltage of 11.07V
almost exactly a 20% drop in light output from reference spec on the chart above.

10 gauge w/ relays
3 feet one way, don't go to and from the switch,
the voltage drop is .72% .086 V drop for a delivered voltage of 11.91V
just a bit higher than the reference spec in light output on the chart above.
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