Trailer wiring to ST1300 - best practices?

Sadlsor

Sadlsor

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Birmingham, Alabama
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2008 ST1300A
Will be picking up my first trailer in a couple weeks, to go behind my 2008 ST1300.
Most of what I read here suggests tapping into existing brake light / tail light wiring out back.
Does anyone use a fuse block? I have one already.
Is this over-engineering? Is there really such a thing?
Does it help or hurt, and how and why?
Next up... as most of the threads are a couple years old, where are some good places to source a hitch and wiring connector?
Southeast preferable, although with UPS it doesn't really matter.
First-time trailer guy here.
Thanks much!
 
Hi Sadlsor
I bought an adapter to go from the bike wiring to the plug on the trailer wiring harness. If you look at the trailer wiring and determine if it’s 4 or 5 wires, that will give you the info you need to wire your plug to the bike.
Yes, in my opinion, they should be fused.
Also, do you want a live wire to the inside of the trailer?
Brian
 
There's a thought process about wiring up your trailer and you're free to choose which way you want to go.

1. You can wire the connector directly into the harness.
2. You can put relays (more than one) in to isolate the trailer wiring from the harness.

#2 is the more laborious route but helps prevent any issues with blowing main fuses / bulbs etc on the bike if there are any issues with the trailer.

This is regardless if you need / use a wiring adapter that combines direction signals with running and brake lights. (depending on the light setup on the trailer)

I have not included any wiring diagrams etc but I can provide some if desired for everyone to critique.
 
As Obo suggested, you need a relay and a separate circuit. I happen to think this is mandatory because I've seen a lot of auto trailer harnesses that look beaten up - and a problem waiting to happen. Without said relay and fuse, a short in the trailer wiring takes out your brake and running light (maybe even indicators), and now you are unsafe at any speed (so to speak). You can buy the harness with the relay built in, or make your own, it's not expensive or difficult.
 
Thanks for that.
I was rather hoping that the preferred method would include separating trailer wiring from the main wiring harness, for the purposes of isolating any potential (expected?) snafus that might (will?) Inevitably occur.
After all, Mr. Murphy lives in my back pocket.
And yes, I foresee adding an interior light, whether automatic when the lid is opened, or even switched in the trunk.
That's how I'd like to proceed.
Keep the ideas and resources coming.
 
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For a light, use a motion sensing battery powered light that comes on when you open it, like this.
 
If the trailer has incandescent bulbs, you will be taxing the stock wiring on the ST1300. It is better to isolate the trailer electrical from the bike electrical so that you never risk loosing the function of the lights on the bike no matter what shorts out on the trailer. The easiest way to achieve that is by installing a trailer wiring isolation relay and harness. The one below works well, is all electronic and is quite small. It also has an additional wire that will transfer 12V+ fused from the battery to the trailer through the same sealed relay box. This wire can be used to run whatever you want in the trailer fully independent of the lights.

They just happen to be on sale right now;
Kuryakyn Universal Trailer Wiring & Relay Harness - 7671 You need the universal one for the ST1300.

You can also make your own if you wish but the Kuryakyn is completely sealed and is small.
ST1300 - Wiring diagram : Trailer Isolation Relay
 
Sadlsor said:
Thanks for that.
I was rather hoping that the preferred method would include separating trailer wiring from the main wiring harness, for the purposes of isolating any potential (expected?) snafus that might (will?) Inevitably occur.
After all, Mr. Murphy lives in my back pocket.
And yes, I foresee adding an interior light, whether automatic when the lid is opened, or even switched in the trunk.
That's how I'd like to proceed.
Keep the ideas and resources coming.
Click to expand...
Did you ever get this done?
I'm not going to be pulling a trailer but I'm going to mount an elevated combination taillight unit with turn signals for long haul trips.
That is why I'm searching for a trailer harness and"plug". While it may not be this exact unit, it will be a similar LED unit mounted on a telescoping pole to sit about "head-high". (minus the lic plate holder)
1677679124955.png
 
Yes, it's done.
However, it's more of a "functional" arrangement, as I haven't run it inside the rear fender yet. The pigtail and connector are wedged between the right pannier and gender for now, so I can't call it finished, only working.
Except then I added Warm n Safe to the battery, and a GPS to the quartet harness, and likely blew the turn signal fuse.
No turn signals, no flashers, and even the GPS doesn't stay on.
Tail lights and brake work on the bike and trailer, and the heated gear heats.
It's shameful, but my working hours leave me exhausted and I haven't taken plastics off yet to troubleshoot.
 
12v. HTH

:hat1:

In a little bit of seriousness though, I don't have a trailer. I do have an additional fusebox under the pillion seat though. Because a trailer counts as a farkle, right? (what? I did say "little bit of seriousness")
 
ad.hom said:
Because a trailer counts as a farkle, right? (what? I did say "little bit of seriousness")
Click to expand...
I would think ABSOLUTELY.
This is one of the very largest "farkles" I could imagine, and it's not for everybody.
In fact, if it weren't for having to haul tools and computers and very large TV monitors and network cabling, etc., not to mention my German Shepherd, I would never have seen myself pulling a trailer behind my bike. Many have suggested a sidecar, but that's not as easily removable, and of course completely changes the dynamics of riding. Not for me.
But I'm adding over 20 thousand miles annually to my old Honda Element, just turned 145K, and I need to give it a rest. And of course, there's the 2x mpg factor riding on 2 wheels compared to 4.
 
One option is having a master circuit for every light on the trailer, and a relay powered by the bike's wiring for each trailer light function. Another is to simply wire each trailer light directly to its bike light, and be sure to use a signal flasher that can handle more than two bulbs.

You can tell a heavy-duty flasher because it will flash faster if a bulb burns out (or is removed), while a standard flasher will not flash with a bulb out. The difference is whether the bulb current opens or closes the contacts. (I'm talking about a thermal flasher, not electronic.)
 
As for what I did - I ran feeds from each turn signal and the brake light to 3 relays.

The 3 relays get power direct from the battery.

I have 1 master fuse & switch between the battery and the 3 relays and another fuse between each bike bulb and the relay.

This isolates all the power from the bike circuits so if I have a short on the trailer I'll blow the main trailer fuse and if I have a relay short issue I'll blow the fuse and hopefully not lose any of the bike's lights.

The trailer running lights are not run though a relay (as I recall) but direct connected & controlled by either unplugging the trailer plug or by the master 12v feed disconnect I put under the seat. I can't recall why I didn't do a 4th relay but there was some reason. :) I think I wanted constant 12v power to the 12v socket in the trailer when the bike was off. I'm aware this could drain the battery if I forgot to "turn it off" and a relay would correct that.

Like @Sadlsor's setup it's not pretty right now but it's functional.

seatgrounds.jpgtrailer relays IMG_1399.JPG

As for a farkle, I'd say it certainly is.

1677724446014.png
1677724486215.png
 
Obo said:
As for what I did - I ran feeds from each turn signal and the brake light to 3 relays.

The 3 relays get power direct from the battery.

I have 1 master fuse & switch between the battery and the 3 relays and another fuse between each bike bulb and the relay.

This isolates all the power from the bike circuits so if I have a short on the trailer I'll blow the main trailer fuse and if I have a relay short issue I'll blow the fuse and hopefully not lose any of the bike's lights.

The trailer running lights are not run though a relay (as I recall) but direct connected & controlled by either unplugging the trailer plug or by the master 12v feed disconnect I put under the seat. I can't recall why I didn't do a 4th relay but there was some reason. :) I think I wanted constant 12v power to the 12v socket in the trailer when the bike was off. I'm aware this could drain the battery if I forgot to "turn it off" and a relay would correct that.

Like @Sadlsor's setup it's not pretty right now but it's functional.

seatgrounds.jpgtrailer relays IMG_1399.JPG
...
Click to expand...
Thanks that's very helpful. I notice that you make no mention of flashers. Are the lights on the trailer LEDs? Or is the capacity of the OEM units enough? My project will use LED tail, brake & directional s .
 
NVDucati said:
Thanks that's very helpful. I notice that you make no mention of flashers. Are the lights on the trailer LEDs? Or is the capacity of the OEM units enough? My project will use LED tail, brake & directional s .
Click to expand...
The relays for the trailer's turn signals will cycle on and off with the bike's signals, flashing the trailer signals in unison, while adding little enough load to change the flashing rate.

LEDs in the trailer lights would likewise add so little load that you can do without the relays completely, but the wiring could still theoretically blow bike fuses if it gets crushed.
 
NVDucati said:
Thanks that's very helpful. I notice that you make no mention of flashers. Are the lights on the trailer LEDs? Or is the capacity of the OEM units enough? My project will use LED tail, brake & directional s .
Click to expand...

Like @Larry Fine said the flashing of the bikes signal lights trigger the relays on & off, thus making the trailer signal lights flash as well. No additional flashers are required.

My bike's lights are all LED.

The trailers lights are currently all incandescent. I do plan to swap them out to LED mostly to increase the brightness. The trailers rear lights are a sealed beam type and you can't upgrade the bulbs as they are built into the housings.
 
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@NVDucati as for adding in an extra set of lights on the bike, if they are permanent then you really shouldn't require relays. Assuming they are LED (and usually are) you can simply wire them into the existing bike lights. Add a fuse if you wish but that's usually not required. My extra rear brake lights on the bike are tied in direct to the rear brake light. No relay, no fuse (other than the one for the normal brake lights.)

You'd only need relays for either a high draw addition or to isolate the circuit from the bike (which is what you want with a trailer.)
 
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