[AgentX]

Hi all...

Will be constructing a wiring harness of my own design on my upcoming rebuild.  Running a Hitchcock's uprated alternator and and h4 in a 6 1/4" bucket, most likely 60/55w to start off with.  Tail lamps are led, no signals or idiot lights at all ; gauge lights are led as much as I can manage.  Bar switch is a super-simple off-lo-hi / horn setup.

I had planned on using the bar switch to trigger relays for lamp power straight from the battery.  Then it occurred to me that the only advantage of this would be 2' shorter wire run plus one less switch for the power to pass through.  (My key switch, in this case.)

The bike will be subjected to a lot of abuse and hostile environments.  So I was thinking the simpler routing of power through the bar switch might actually be an advantage, with fewer contacts to corrode or otherwise go bad and easier troubleshooting when required.

Unfortunately I won't have the ability to measure or practically test the setups side by aide before building the harness...any thoughts on whether the relay setup would offer any practical benefits in my case?  I know theoretically that it would give a brighter bulb...but would it be a tangible, noticeable difference?

Along the same lines, what about a relay controlled from my kill switch, allowing a really short, direct wire run from the battery to the coil?  Sounded good on first draft, but may just be more complicated without offering much in exchange.

Thx!

[ace.cafe]

If the wire and switches used are of sufficient gauge and rating to provide minimal voltage drop and carry the current, then there is little or no value to using a relay in the circuit.

The advantage of using relays comes from being able to use lighter switches and wire gauges to actuate the relay coils, instead of carrying the load currents.

[Blltrdr]

I built a harness for my Bullet a quite a few years back using Pete Snidal's Brit rewire page http://www.angelfire.com/biz/snwvlly/bikes/negwire.htm. I have my wiring diagram over at Ace's site. Have had no wiring issues except for replacing the rotary switch and adding a relay for my new horn. I am also running my H4 with the wires from the Ducon switch with no problems and no relay.

[baird4444]

I converted my 5.5" to an H4 with no relay and electrickel issues.
werked fine with no burn or arching in the swith for years.
              - Mike

[AgentX]

Thanks, guys.  To elaborate, I had installed a relay when I installed a single-beam HID setup.  The high initial draw of HID is allegedly not good for switches. But with the new wiring harness, I'll be going back to H4.  (Not that the HID was unsatisfactory as a light...I just didn't want to face a problem with it overseas and be unable to get a replacement lamp.  H4 is always easy to find.)

There's a lot of testimony online about relays making lights brighter and decreasing wear on switches, etc., but when I looked at the schematics I have drawn for my own bike, it just didn't really seem to be accomplishing much in practical terms in my case.  Maybe a connection or two less, but I didn't see how that would really result in any major loss of output from the lamp; plus, it added a bunch more potential points of failure.  Given that my bike's likely to see harsh environments and over-sea transportation, keeping things to a minimum really seems like the best idea.

In my case, the wires are 16ga, which according to my chart here should be overkill to carry the required current.  I think I will fuse at 10 amps just to be cautious.



Connectors are all going to be high-quality automotive stuff; I'm actually planning on using Weatherpack for my exterior block connectors if I can stomach the price of the crimper.  Got a few other sealed options I'm also considering which may be compatible with the crimper and dies I have, too.  Switch is a cheapo generic bar switch (hi/lo/off and horn only) but it's super-simple and should be easy to clean and/or replace if required.

Thanks again for your input and reassurance.

[azcatfan]

Thanks, guys.  To elaborate, I had installed a relay when I went to the single-beam HID setup I had used to use.  The high initial draw of HID is allegedly not good for switches. But with the new wiring harness, I'll be going back to H4.  (Not that the HID was unsatisfactory as a light...I just didn't want to face a problem with it overseas and be unable to get a replacement lamp.  H4 is always easy to find.)

There's a lot of testimony online about relays making lights brighter and decreasing wear on switches, etc., but when I looked at the schematics I have drawn for my own bike, it just didn't really seem to be accomplishing much in practical terms in my case.  Maybe a connection or two less, but I didn't see how that would really result in any major loss of output from the lamp; plus, it added a bunch more potential points of failure.  Given that my bike's likely to see harsh environments and over-sea transportation, keeping things to a minimum really seems like the best idea.

In my case, the wires are 16ga, which according to my chart here should be overkill to carry the required current.  I think I will fuse at 10 amps just to be cautious.



Connectors are all going to be high-quality automotive stuff; I'm actually planning on using Weatherpack for my exterior block connectors if I can stomach the price of the crimper.  Got a few other sealed options I'm also considering which may be compatible with the crimper and dies I have, too.  Switch is a cheapo generic bar switch (hi/lo/off and horn only) but it's super-simple and should be easy to clean and/or replace if required.

Thanks again for your input and reassurance.

Dayum!  Copied and saved, I love stuff like this, this forum is awesome...

[AgentX]

Dayum!  Copied and saved, I love stuff like this, this forum is awesome...

I just grabbed it off Google, bro... 

[barenekd]

I added relays to my 2011 G5 for the headlight, 7" H4, and ran a sealed beam also, (not together). Brightened the light considerably. Ran the 16ga power wire from the battery through a fuse to the relays.
Bare

[AgentX]

See? That's the damned problem.  Every time I decide on something, someone credible pipes in and says "they worked better for me!"

[Chasfield]

I'm with Ace on this. Keep it simple but over engineered! Go for heavy duty wire, high grade soldered and crimped connectors, plenty of heat shrink sleeving, a reg/rec that can handle twice what will be asked of it, careful routing/support of wires etc, etc.

My car has plenty o' relays buried under the dashboard. I have to thump it to make the lights come on.

[AgentX]

Go for heavy duty wire, high grade soldered and crimped connectors, plenty of heat shrink sleeving, a reg/rec that can handle twice what will be asked of it, careful routing/support of wires etc, etc.

Oh, definitely.  My first attempt at making a wiring harness was, shall we say, a learning experience.  It worked, but it was ugly and had some real weak points.  (I went from zero to full harness all on my own with little to guide me...I'm just glad it actually worked at all!)

This time around, I have the nice adhesive heat shrink for where it's warranted, plenty of good, fresh 16ga wire, enough connectors and a better understanding of how to properly crimp them, etc.  Have a Boyer Powerbox for the reg/rect, an up-rated alternator, an Antigravity battery I scored on the cheap, and other nice-to-haves.