Motorcycles, Electronics, and Upgrades — Considerations and “How to do it Right”

This entry started from a posting I contributed to on the HDForums site. I decided to expand upon the various talking points there into a more full-fledged discussion about the hows, whys, and considerations of adding electronic gadgets to your ride.

My experience involves a 2016 Harley-Davidson Heritage, so specific examples in this post may involve this particular maker and model.

Let me add here, early, that I welcome suggestions or criticisms of any of the information I’ve posted here. I am not an electrician, therefore my advice is from a layman’s point of view. I am a programmer, however, and logical thinking and design are within my area of expertise.

This article is lengthy and was written over several days. If you are a “tl;dr” kind of person, you can jump to the last section for a summary list of steps.

Basic Planning

Each additional electronic gadget you add to your bike will have a power draw. Each motorcycle model will have a power plant producing only so much power. If you’re adding a single item, you’re probably fine. If you’re adding more of the following: GPS, USB Charger, Stereo / Amp, LED strip/pod lighting, camera systems, trailer wiring … you have to consider the draw of each of those items and what available output you have remaining after the existing (stock) usage. You are already powering headlights, speedometers, tachometers, passing lamps, blinkers, tail lights, etc.

Most manufacturers of electronics put the voltage and min/max amps on their product and/or their packaging. Be sure to check for these numbers and available output when planning your calculations.

This shows a 24V input (you’ll be 12v on a motorcycle) and a draw of .43 amps.

If you find your numbers are too high, consider replacing incandescent lighting on your bike with LED’s. This would include headlights, passing lamps, blinkers, tail lights, brake lights, etc. LED’s have a much lower power consumption than other lighting types.

Remember that your battery has a certain amp-hours rating. This means how many amps can be pulled in an hour from the available storage. If you see .43A in the picture above, that means “This device, if constantly on, will use .43 amps perh hour.

Switched or Unswitched?

On your motorcycle, the headlight doesn’t come on unless the bike itself is on. This is an example of switched power. The headlights are on a “switched circuit”. If your bike has an alarm, however, and the bike is knocked over the alarm goes off. This is because it is on an “unswitched circuit”. The unswitched circuit has a direct connection to the battery, providing constant power. The switched circuit requires a separate switch to close (like turning on the bike, or a toggle switch) to complete the circuit and provide power to the device.

On my Heritage, the unswitched power is easy… I can just tap the battery. For the switched power, however, there is an adapter that must be purchased and added to the bike. Here is an example, though mine is a 6-pin, not a 4-pin. My Innovv K2 camera right wants switched and unswitched power.

I purchased an “accessory switch housing” that has a Heritage fitment and has space for three switches, one included, two must be purchased separately. My passing lamp switch was a toggle behind the forks, and I hated reaching for it. So this became switch #1 in the set and required very little work since the wiring was all in place, and I just had to move it a bit higher. This didn’t change the power draw of my ride, just changed how I turn on the passing lamps.

The HD “accessory switch housing”. Comes in chrome or black for Harley. (Though the black, I think, only comes for the left side!?)

The second switch I use for “switched power that I control” rather than “switched power that the bike controls”. This means that the one side of the switch receives constant power, and those devices that I want to turn on (even if the bike isn’t on) such as my LED lighting and the stereo amp, those devices receive power when I flip the switch and complete the circuit.

Some devices require (or support) both constant and switched power. Consider a stereo in your car that maintains the memorized station numbers. The stereo itself doesn’t come on until you switch on the car, but the constant power maintains the memory. In this case, that device would have three wires: red (positive power), black (ground) and another color (yellow or blue or other) for the switched power!

Disconnect the Battery!

When dealing with electricity, even at just a low 12 volts, it’s always best for your protection as well as your bike and other electronics, to disconnect the battery. Always disconnect the negative terminal first, and ensure any connected wires stay well away from the battery, maybe separated by a piece of plastic or other non-conductive material. Next, you can disconnect the positive terminal, also keeping wires away from it. When reconnecting later, reconnect positive first, then negative last.

Wire Placement

This is probably the most difficult set of decisions if you have multiple devices that require power. If you’re wiring a simple USB charger, you might end up just going to the battery and deciding is easy.

If you’re adding as many things as I have, you’ll need to plan it out! Three switches from the handlebar, USB charger, and my Innovv K2 front camera… that’s 9 wires! In my case, I get them cable-tied together near the beginning, snug them up, add more cable ties as I get to the end. For my Heritage, the best place is to run them was under the left side of the tank, through the frame and into the battery area, then back out of the frame and into my saddlebags. I have too much wiring and connectors, etc. to put anywhere besides my bags.

Also consider, when placing the wires, to avoid sharp edges that might rub and short them out, how hot it will be in a given place, and avoid any moving parts that could be damaged if a wire gets tangled up in them!

Cable Protection / Heat Shrink

Wrapping the wires in heat shrink or plastic cable protection is advised as this can minimize their exposure to heat, water, bugs, etc. Just never use the heat gun and shrinkwrap them until you’re sure you’re done! Otherwise, you’ve wasted money and time. Getting those back open isn’t fun; you have to be careful not to cut the wiring inside.

If you know you’ll make changes later, you might consider skipping the heat shrink altogether, or maybe wrap the wires later with a heat shrink you’ve sliced open and just hold with simple electrical tape. There is also pre-split plastic cable protection you can use, too, though it isn’t waterproof.

Using spade connectors and their matching female counterparts (or bullet male/female connectors) can make it easy to disconnect, and simply protect with a quick wrapping of electrical tape. Many of my connections are these, especially where I needed extensions to compensate for pre-existing wiring that was too short.

From under the seat, to the saddlebags, my wires are in heat shrinks. Actually applying the heat gun, though, is one of the last things you’ll do. (I had to feed new wires through, undo, re-do, multiple times.)

Connections and Serviceability

I stated above that all my electronics/wiring goes in the saddlebags. Well, what if those need to be taken off for servicing, like a new tire or a belt replacement? It’s important that a service tech is able to move all that stuff out of the way to do their job. (Or yourself, if you’re a wrencher.) In my situation, I can remove the electronics bundle from the saddlebag and at least set it on the seat. For my trailer hitch wiring, though, that runs out the back of the bag. How will I remove the bag if that’s in the way? The answer is “waterproof connectors”. My trailer wiring is set up for 6 wires. The standard five, plus a hot wire (that third switch on my handlebars!) that powers the brake controller. Using a connector like the one pictured below can allow the connection to be removed for servicing, but without having to dismantle the trailer plug from the hitch assembly I have.

A waterproof connector. 6-pin, so not exactly what I need for a 7-wire setup. I like these style pins, though, because you can crimp to the wire insulation, too, making a much stronger connection.

Main Power – Disconnect

I stated above that you should disconnect your battery. This is true, but at some point, you’re going to have to pull the trigger and feed power to your devices. From the bike, I knew I’d need three main wires: constant power, switched power (via the HD adapter) and a ground wire running to the frame. (In my case, the main ground runs to the battery, not the frame so I could test without triggering my bike alarm! I did trip it, once, and in the house it’s ear-splitting!)

To enable the hookup from the bike to my fusebox, I decided that if I needed three wires, the simplest thing to do was to use a standard 110 grounded plug. Yes, in my case AC isn’t DC, but it worked fine. I used the larger pole for constant positive, the other for ground. The third pole, always the ground for a 110, I used it for the switched power. These can be found here and here or at pretty much any hardware store. Thinking about it later, I probably should’ve put ground on the true ground pole, but in the end, it doesn’t really matter that much, as long as you wire it the same on both sides. Not like I have to adhere to building codes!

Note: Always use the female connector (on the right side, below) for your main power from the bike. With nothing sticking out you greatly reduce the chance of getting shocked.

Simple replacement plugs make excellent main power disconnects!

Use a Multimeter

I’m a programmer. That means I must test things, progressively, as I go along. You don’t want to get the entire code project completed, it not work, and you have no idea why.

As I put in crimp, or a connection, or a circuit or made any change, I used the multimeter to test for either voltage or continuity. I have a simple multimeter from Harbor Freight that will beep when continuity is in place. It cost me $22, but has saved me hours already by testing early and discovering that one of my crimps didn’t hold, but wasn’t obvious.

Test early. Test each circuit as you build them. Then test again. I stated above that I am not an electrical engineer. You probably aren’t either, so do what I did: watch YouTube videos on how to use the multimeter. I suspected I could test for continuity (else why would the thing have a battery), but had no idea where to set the dial or what the symbols mean.

Using a Fuse Block

I have a LOT of wiring I put together for my winter project. I have the following components:

  • Amp for the new speakers
  • Innovv front/rear camera system / DVR
  • LED strip lighting
  • USB charger on the handlebars
  • Two handlebar switches
  • Trailer wiring

I ended up purchasing an excellent fusebox. Because I knew that there were items on the constant power like the cameras and amps and trailer wiring, but also items on both or only on my switched power, I needed something that supported multiple circuits. (Truth is, I could’ve used FOUR groups, plus ground, but there’s nothing like that in the small size I needed.)

I ended up going with a fuse block from Blue Sea Systems. I really, really like it, and the size is good. At $57, it really gave me a good, clean option for building up my wiring. The space I have available in my saddlebag made it a little crazy looking when the wires were all installed! It also comes with a cover to prevent zapping myself reaching to the bags.

It *seems* messy, but it actually is quite organized. I do have a little more cleanup work to do on it. (Shown without the cover that you’ll definitely want to use.)

I started with a project box, that I could seal components into, and my initial (single circuit only, no ground) fuse box worked on. With the new one above I ended up cutting down and sanding a piece of plywood. This allowed me the flexibility to change my mind on screws I was putting into the board. With the PVC project box, I had to drill pilot holes then grind down the screws once I had them in place. With the 3/4″ plywood, I had plenty of screws the right size.

You can see, at the top of the photo, a small distribution block. Each pair of screws is separate from the others. This allowed me to make clean, protected connections between things that just wouldn’t work on the main fuse block. For example, on the right side is a yellow connection. This is the switched wire from the adapter I installed on the bike and is the true motorcycle key switched power. I only needed it for the camera system, so tying up an entire portion of the fuse box would have been a waste.

The red/black combo on the top left side is the 12v switched power to the trailer’s brake controller. It only has the one use, so again, not tying up a fuse section.

That second switch on my handlebars causes Block B (the bottom section, constant power) to feed power to Block A (the middle section) when I flip the switch. The top portion is all grounding, and was the main reason for purchasing this fuse block; I wanted to be able to cover everything for safety.


Admit it to yourself: You are not going to remember what everything is in a week, a month, a year. I took the picture above because it’s going into Photoshop and is a basic start for documentation. I will be laying out what every wire is for, where it goes and what the fuse amp requirements are. (One of them is just a 1 amp fuse! Important to remember which that is, so as not to put a 10amp in there by mistake.)

As I was completing the wiring of all things to the fuse box last night, I ended up with two wires I could not remember, for the life of me, what they were for. Turns out they were for the USB plug, and after thinking for 10 minutes about it, I was able to figure it out. (Another good reason not to do your cable ties or heat shrink too early! Glad I hadn’t.) Having early documentation, though subject to change, would’ve helped me avoid that issue. Or if later a poor crimp turns loose, you’ll have an idea of what it was for. Just print out your documentation, stick it in a ziplock bag and toss it with the wiring for you or anyone else to view later as needed.

Miscellaneous Notes

Wire crimps

Crimping your wires into a spade, round or U-style terminal is a big part of any wiring project. I can’t tell you how many connectors I’ve had to re-crimp after some minor movement. A friend pointed out to me that Vice Grip brand pliers have a great crimp area in them. I used this trick while fixing a couple of my poor crimps, and it worked wonderfully. I was able to get the leverage needed. I struggled with my simple, flat crimpers sometimes offsetting and cutting through the nylon coating. The vice grips don’t ever offset on me!

The area circled in green makes an excellent crimp and the Vice Grips provide excellent leverage.

Carry Spare Fuses

This is your new wiring job. You may have made mistakes. If so, you’ll want to be able to correct the issues and replace the fuse roadside. That means carrying some spares. I would recommend at least one fuse of each type you in place. Multiple if you have repeating amp fuses. I’m carrying 2 x 10amp extras because I have more of those in place than any other.

Changing your Mind

Later, you might decide you don’t like the way you’ve built something out. Using good planning and keeping serviceability in mind, you should be able to make small changes without drastic effect. I am already considering a larger board, where I can place everything on one side. It’ll take up additional room, but I am okay with that. Right now, if I don’t change, the board fits nicely along the side of the bag.

My early capacity testing. It worked good initially, but once I added all the wires and the physical devices to the other side of the board, it still fits, but not as cleanly. Wires are catching, etc. now when I attempt to remove it and return it. This positioning didn’t leave much room for “board overflow”. I might use a longer board, turn it lengthways along the left or right of the bags instead of to the front side as shown here.


  • Plan everything out ahead of time.
  • Prepare for devices that require switched and/or unswitched power.
  • Disconnect your battery to protect it and yourself.
  • Layout your wiring plans, where will it all go, is everything long or short enough?
  • Protect or Heat Shrink your wire bundles.
  • Use connections where possible for serviceability.
  • Provide at least one connection for the main power, ground, and switched power.
  • Testing all connections with a multimeter will save you lots of time later.
  • Consider using a fuse block if you have a lot of wiring to do.
  • Document! You will not remember all these wires later.
  • Extras:
    • Ensure you have good crimps.
    • Carry extra fuses of each amp rating you’re using
    • Keeping “serviceability” in mind may along you to make changes later.

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