Adding a Centech AP-1 To The Road King…

As I mentioned in my previous entry where I described the Bushtec hitch installation, adding yet another hot lead to the Road King’s electrical system turned out to be the straw that broke the camel’s back:  it was time to install an auxiliary fuse box.  Here’s the finished product, just to dispense with the suspense:


I would have included a “before” photo, but I was embarrassed by the whole mess.   I’d done a pretty good job of tucking the various in-line fuse holders and wiring around the perimeter of the battery box, but it was still a rats-nest of wiring and there was no hiding the collection of five post terminals stacked-up on the positive side of the battery: it was simply driving me nuts.


BMW After Installation of the AP-2

I was reminded of the wiring nightmare I found when I pulled the cowlings off my ’04 BMW R1150RT just after buying it from previous owner, as it had an intercom, driving lights, heated gear, GPS, and a radar detector all tied into various cigarette lighter plugs and the battery.  I ended up installing a Centech AP-1 auxiliary fuse box in the tail cone of the bike along with the AutoCom controller to get it all sorted out and had all of the wiring routed along the sides of the frame in plastic wire housings.  So, I was pretty sure it was time to put a Centech in the Road King.


Custom Dynamics Load Equalizer

What I had to contend with was finding a place to put the somewhat large box for the trailer lighting containing four micro relays, the two-piece 8-pin connectors and the connector for the harness that runs to the hitch for hook-up to the trailer. Ideally, it needed to go in the small dead space behind the battery under the seat; however, that already was home to the Custom Dynamics load equalizer box with its two-piece 8-pin connector.

My initial solution was to stuff the trailer’s relay under the right side cover with the turn signal / security control module and ABS system.  However, once I had it wired-in I got quite a surprise when I tried the turn signals: those micro relay switches were the loudest darn relays I’d ever heard!  CLICK, CLICK, CLICK, CLICK; Yikes!  Moreover, the tight quarters under the right side cover put the housing right up against the frame and cover, which amplified the relay clicking sounds.  No doubt about it, that sucker needed to get buried under the seat… and then some.

The “then some” was filling the cavity of the plastic housing with the four relays with silicone and then sound insulating that with a couple scrap pieces of bicycle inner tube and then enclosing the entire thing in another piece of scrap inner tube.  It’s definitely weather-sealed at this point, but it’s also a lot more quiet.  Of course, with the trailer’s relay box under the saddle, the Custom Dynamics load equalizer now had to go under the right side cover. So, it also ended up encapsulated in a rubber covering to keep it protected from the elements.  All-in-all, it worked out pretty well.

Photos Below:  In the annotated pictures the color coding works like this:

  • The Orange box shows where the trailer’s relay switch is located
  • The Orange lines represent wiring harness / power routing
  • The Yellow box shows where the Custom Dynamics load equalizer is
  • The Yellow lines represent the power & ground wire routing
  • The Bright Green diamond & lines represent Debbie’s heated gear wiring
  • The Light Blue diamond & lines are my heated gear wiring
  • The Pink diamond and lines are the power to a DC outlet for my phone/GPS that’s located up next to the headlight.
  • The Red & Blue diamonds / lines represent the Pos / Neg leads from the battery to the Centech AP-1 auxiliary fuse box.
  • The Green box represents the Centech AP-1 auxiliary fuse box.

DSCN0161 Slide1DSCN0162 Slide1_3

And, here’s the heart & soul of the now well-organized electrical accessory tie-in to the bike’s battery. Same color-coding scheme as above.

DSCN0160 Slide1_2

ap1The Centech AP-1 is a pretty slick little fuse box, albeit a bit pricey.  However, for the money it’s the best of the bunch of several other equally pricey auxiliary fuse boxes in that the four mounting posts raise the box so you have a place to route the wires on their way to the positive and negative lug-less terminal strips along each side of the fuse box.  The box is somewhat deceiving in that the three fuses in the middle of the box each support two terminals, such that you can wire up to eight (8) devices to the fuse box supporting up to 60 amps.  That’s more than the bike’s alternator can supply and far more than I need.  Our heated jackets draw 6.5 amps each, gloves about 2.2 amps, my Samsung SmartPhone / GPS draws about 2.1 amps, the Custom Dynamics load equalizer is equally low-draw (

I attached the fuse box to a small piece of sheet metal and then attached that to the motorcycle’s security siren module with Velcro.  That makes for a secure installation, but it also makes it relatively easy to pull off when I need to add or remove accessories.  I need to shorten-up the wires and wire housing to tidy-up the left side compartment, but I think that’s about it.

I’m a much happier camper now that my electrics are all nicely organized. As for those noisy relays, they’re not as noisy as they used to be but they’re still pretty loud when the bike’s not fired-up.

And, yes… I did take the rig out for a very short trial run last night.  I could definitely tell I was pulling a trailer, as there’s a very different feel to the bike even with the very secure Heim joint connection.


About TG

I've been around a bit and done a few things, have a couple kids and a few grandkids. I tend to be curmudgeonly, matter-of-fact and not predisposed to self-serving chit-chat. Thankfully, my wife's as nice as can be otherwise we'd have no friends. My interests are somewhat eclectic, but whose aren't?
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2 Responses to Adding a Centech AP-1 To The Road King…

  1. bleednate says:

    Great article. Recently bought an ’03 R1150RT. It has a Centech AP-2 with a garage door coder/decoder as well as a CPT to double USB to power those which require USB. Last owner had an Android phone which charged just fine, but my iPhone 5 nor my iPad Mini will not charge with this configuration. Any suggestions?

    • TG says:

      Thanks for the kind words on the blog entry. If you’ve confirmed both USB outlets are still working with a multimeter or by plugging in other non-Apple devices, you might want to shoot a note off to the folks at Current Logic to see if there might be some type of technical incompatibility issue before simply replacing the unit with something else. Ride safe!


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