Rudy's GL1500 Photo
Auxillary Power Wiring
revised February 26 , 2008
For 1100 owners, also see the 1100 addendum graciously
provided by Dubswing for some routing and mounting
ideas for that model.
Reference pages are
not intended to provide full procedural guides. They are merely
photos and comments, many submitted by others who have contributed them
out of interest in helping others see what might help them in the same
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If you are like most of us,
soon after you get your bike
you want to add "stuff" to it. Some of that "stuff" will be
stuff. If you bought your bike used, chances are it had at least
some electical add-ons that came with the deal. Most times
you see that the guy who did the add-ons was not an electrically
trained individual. Also, most times the manufacturer just wants
get things put on the bike as easily as possible so they don't have to
lot of support time training you how to do it right, even if they know
how, which is many times not the case.
Also most times the bike owner and the accessory supplier has NO idea
what else is already on the bike and what power strategy was used to
get those things going. It's almost like you try adding things
test the bike to see if it's ok. If it seems to be, you go on
it was ok. Sometimes it is, and sometimes it isn't. And
that doesn't mean it will stay that way. That is why most
knowledgable motorcycle advisors (including me) recommend that
when you get a used bike, you should remove all existing add-ons and
get back to stock, particularly if you already are experiencing a
problem which is when we help-type guys usually hear about it.
Then you can
begin to move forward from there.
That is good advice because it tells you if there is an inherent
problem in the bike's own systems before you try to add to a possible
and it gives everyone a known starting point as a reference.
Whether your bike is new or not, you need to control the power
consumption or that consumption will control you one way or the
other. Often by surprise and at the worst time. Bike
manufacturers put the accessability points in the middle of the bike so
you can go both ways to hook up stuff. But add-ons rarely get
placed in the middle of a bike where the power access is. So
people commonly add new loads and tap into the wiring where they think
it will work without much regard to the new loads they are adding.
Stock Power Access Locations:
When you add certain accessories, the add-on manufacturer often
instructs you to take it directly back to the battery for power if they
tell you anything at all or they tell you to kluge into the existing
harness with 3M blue squish splices.
In the case of high current and critical items, it is necessary to
get enough current directly to the product. Good examples of
these are running lights, trailer isolation relay packs, cigarette
lighters, audio power amplifiers and heated clothing to name just a
few. Unfortunatley, this often un-coordinated symphony of connections
can end up with WAY more terminals at the battery than you can
get bolted on and the cluster of wires there is confusing, messy and
often times dangerous.
The bike's fuse block has an Aux Power connection and fuse but the aux
terminal point is only for 5 Amps and that won't handle even ONE of the
large current add-ons. I commonly see guys with this aux fuse
changed to 15 amp fuses to try to handle the add-ons. It works in
most cases but then you may have consumed all available capacity of the
Aux Power circuit so you are done anyway, no more switched add ons
possible and you don't know how much current the fuse block was
designed to deliver at the aux terminals so you mught be creating a
fire hazard right next to the gas tank. As stated above,
the bike manufacturer's choice to place the access location on the
middle of the bike is understandable but when is
the last time you added an accessory to the middle of the bike???
You normally add accessories to the
front of the bike or the rear of
the bike but not the middle!!!
So why not solve everything once and for all and get what you need
where you need it permanently with enough capacity to grow, handle all
easily and make NO out of spec loads on the stock minimalist electrical
Let's get the power safely and conveniently delivered to where it needs
to go with only TWO battery connections for everything and TWO low
current connectins to the Aux terminal on the fuse block. (only
one of each is needed if you are only going to do the front or the
but not both, but why put off the inevitable?)
What goes in the front?
What goes in the back?
- High output running lights
- Rings of fire.
- Air Horns
- Cigarette lighters
- Heated clothing outlets for rider
- GPS units
- Media players
- Security devices
- Alternate communications devices
- Additional show lights
- Relay power packs
- Power Amps
- Cigarette Ligher arrays
- Passenger heated clothing outlet
- Vanity lights
- Trailer isolation kits
- Additional lighting
- CD Players
See what I mean?
What I do is split the bike into two main, high current,
direct-to-battery circuits. One to the front and one to the back.
I wire a 30 amp fused pair of wires right off the battery
(10 ga +12v wire and a 10 ga ground wire) to the front left
and a second one to
the rear main box for things in there. I never rely on the bike frame
for a ground. For the cost of one extra wire, why would I invite
problems with corrosion and unknown capability and voltage drops
This way I know what I'm getting and from where and how much I can
count on it and a very easy means of checking the thing if I ever have
a problem, day or nite.
Then I run a pair of wires from the auxilliary power terminals at the
fuse block to those same places to drive the relays with, as shown
Red is +12 Volts direct from
the battery fused through a 30 Amp fuse right at the battery for each
direction forward and rear.
Green is a new high current
ground directly from the battery in both directions, forward and rear.
(shown black in the schematic below)
Cyan is a jacketed pair of
wires coming from the Aux Power terminal on the Fuse Block to run the
relays, front and rear.
Next I add a 30 or 40 amp sealed relay at each end (one under the
fairing pocket and
one in the trunk). I hook the coils of the relay to the aux power
wires and feed the 30 amp battery hot to the commutator of each relay
through a second 20 amp fuse. This gives me battery grade power,
switched at 20 amps and unswitched at 30 amps at either end of the
bike. At the switched power contact on each relay, I then add
accessory that I want each with their own fuse as if they went straight
to the battery.
If you want to use a battery tender to keep your battery charge up and
still have a high amperage output cig lighter for things like an
compressor or whatever, you can hook it up to the 30 amp
side. Otherwise just put it on the switched side.
All aux accessories connect either front or back this way and the
bike's 5 amp aux fuse only has to run the two relay coils.
Maximum functionality with minimum load on the existing system that way.
Here is the wiring diagram using bullet style quick connects in the
front and using a terminal block in the rear box for convenient
connectivity without a lot of clutter.
I do this first thing on most bikes I own. It saves me from
aggravation when adding things, cludged wiring and mystery electrical
problems later on.
Yeah it's a bit of a hassle doing that. But only ONCE.
If you do that, be SURE to use that cauregated and slitted plastic
ducting around the two main +12 wires off the battery. Actually,
that for every +12 wire I add.
Finally you add a bouquet of bullet connectors to the ends of the
unswitched +12, switched +12 and the grounds at front and a
terminal block in the rear and
viola, plug and play all day, safely and easily.
Nice thing about this system is that it will never become obsolete
and you can choose to ignore whatever you alreayd had wired on
the bike until you have time to trace it out, remove it and re-attach
it to the new system becuse the new system makes no new loads (device
demands for power) on the stock wiring or fuse block (ok 2 relay coil
loads on the aux circuit... about 1/2 amp total).
Here are some shots I made of my setup:
You can see I have not yet gotten the existing wiring down to two
terminals only. Thats the nice thing about this, you don't have
Here you can see the seperate ground wires. I will be changeing
that large ring terminal next time I get some.
Here are the two 30 amp fuses. One has a cover. The other one
will be getting changed to that soon as well. You want these as
close to the battery as possible.
You should shim the wires that touch the frame with some insulation
like rubber or fish paper.
This is a top view of the bike, looking down to see the rounting of
some of this.
Taking the above picture I have added lines for the wiring paths for
clarity. Doesn't matter if you follow this literally or not, it's
just what I did.
The yellow line path is the conduit path for the raw 30A line to the
front left fairing pocket.
The red line path is the conduit path for the raw 30A line to the rear
box right side entry point.
The 10 ga ground wires pretty much tag along the same path.
Here is what the power wiring it looks like as it enters the rear box
under the backrest cover under the seat.
Here it is with the cover removed. Note that the ground wire has
it's own hole and is kept seperate from the conduit and it's raw +12 V,
30 amps, just to keep things friendly in all concievable
situations. It's corrosion, vibration and abraision that causes
problems with bike wiring. This addresses two of the three.
The power to the fairing crosses over the bike at the saddle and goes
along the left side and under the left fairing pocket along with the
Aux power control wires.
(that black box with the white wires is the audio line-in
isolation transformer for the wired in FM modulator under the seat)
Here is where it enters the left fairing pocket along with the Aux
Power control wires next to the CB.
You can also see my audio system cheater cable here.
And finally the jumble of wires in the left fairing pocket area.
Now for the Aux Power routing... again it goes fore and aft for control
of each 30A section.
You connect it at the top of the fuse block under the left side panel
on the bike.
The plastic conduit you see the control wires wrapped around contain
the two front speaker wires from the power amp in the rear box, not
power in this case.
The rear Aux Power control wires and the speaker wires enter the
rear box from the bottom of the left side of the bike.
The third wire is just the passenger headset plug tucked out of the way.
Here is the same shot without the rear cover on showing the entry
points for the Aux Power control wires and the speakers from the front.
Inside the rear box... the 30A power and ground enters the box on
the right side and goes up the wall to under the 3 outlet Cig Lighter
That area is used as a junction box to tap off for the always hot, cig
lighters and it's associated 20A fuse.
Then the raw 30A power and ground wire joins the rear speaker wire and
the rear right speaker out from the radio and
crosses over to the left side of the box in a low rib along the back
wall so nothing sticks out or gets rubbed or abraded anywhere
No loss of space whatsoever..
Here is what it looks like with the carpet in place. Where ever
possible, existing screws were used for mounting the harness and relay.
Everything in the trunk attaches to the terminal block as shown in the
schematic, above. No fork lug terminals are used here, only
type terminals so that in the event of fibration looseness occurring,
things don't drop loose.
I have made a clear lexan cover for the screws, not shown here but that
is why there are threaded standoffs for the terminal block mounting
The red and gold wiring you see at the bottom is from the front
speakers. The upper wires come in from the middle like they do on the
One nice thing about how I mounted the amp is the angle of the backrest
makes a nice wiring space for the hookups and the amp takes minimal,
least critical, space from the box storage.
Again on this side I use the hidden area on the side as a junction box
and you can barely see the 40 A relay down there pointed to by the
It is mounted to an existing mounting screw. That is also where
the wiring goes to the passenger's side tray where I have mounted the
Gerbings controller and quick connect for the passenger's heated
clothing under the swing down door.
Remember that the fusing and loads I have on my bike are based on
having substantial power available to meet those loads. If you
have smaller generating capacity, you may need to drop the raw and
switched main fusing down some to match. For example, the worst
my system could ever see from my fusing plan is 60A peak, worst
case. My system can handle a short load of that duration because
I have a 90 Amp alternator. If you have a 35 amp alternator, you
might want to consider using a 15 amp raw fuse and a 10 amp switched
fuse to keep things safe and to limit the peak worst case to 30
amps. Even so, I would have a 33% reserve capacity where the 35
amp alternator would only have a.15% peak load reserve. And that
is not counting ANYTHING else but the accessories being used by the
bike at the time. I know I could still run my bike in the reserve
30 amps but 5 amps for the whole bike?
Don't think so. You can only use what the bike was not using in
the first place for the add-ons and then you must fuse for that which
you have left. It's not hard but you have to do the math to be
safe and reliable electrically. See the next section about loads
on the bike.
About loading your bike
Since we are talking about loads, we also need to talk about
sources. Your battery is not a source, it is a storage device
which acts like a source for the short term as seen by the loads.
Loads are all of the things that consume electricity.
The source is the charging system which includes the battery.
There is no free lunch in energy. You cannot consume more than
you generate. The battery has stored energy that got there from
an energy generator (the alternator, or a charger). The battery
is similar to a lake with water in it. If rain (alternator)
fill it faster than the spillway lets water out (the loads), the dam
will eventually run low or dry. If you can't
reduce what you let out, you must increase what you put in.
Making the dam bigger won't solve the problem either, only delay
it. In addition an old dam can fill up with sediment and develop
leaks so eventually a new dam (storage device aka battery) will be
needed to give enough short term capacity needed to supply the
downstream load at startup.
For this reason it is easy to slowly add loads to the spillway
that you don't notice right away reducing the water level.
Additionally you can have generators that don't fill the dam like they
used to and that can lead to the same thing as if you had a low rain
year but you didn't notice it until the spillway started getting too
low to pass water. Bad time to find out. That is one good
reason to have a voltmeter on your bike so you can see what the dam
(thing) is doing.
So ideally, you need a source that has more generating capability than
will ever be needed for the spillway runoff and a lake deep enough to
store for short term demands that has not yet gotten too shallow to be
Your loads are usually a constant so that is good if you don't keep
adding beyond your generating means.
The battery is just storage that is deteriorating every day in it's
The alternator is your souce that must keep up with all of this at
minimum even though it too is deteriorating at a much slower
rate. (bearings, brush wear, armature wear and brush dust)
How to assess your
It behooves you to do a load assessment so you know how much energy you
need to generate. You can do it easily with a calculator in
either amps or watts.
Watts is nothing more than energy (work power) made up of volts (in our
at 12v) and amps (the rate of flow) multiplied together.
So if I have a 10 amp load, I simply
multiply it by 12 (v) and get 120
If I know any two of the three pieces (volts, amps, watts) I can
get the third piece of information.
For example lets say I know how many watts a 55 watt headlamp uses
else do I know? I know that the volts will always be calculated
at 12 volts.
So to get the amps, I just
divide the 55 watts by the 12 volts
and get 4.583 amps or about 4 .5 amps for one halogen lamp
If I wanted to figure out a safe but functional fuse to use for that I
would add about 20% to the amps so that would come out to 4.5
amps X 1.2 equals 5.4 amps.
Since fuses come in common sizes, I would have to take the next size
up. They are typically 5, 10, 15, 20, 25 and 30 amp automotive
In this case I would have to take a 10 amp fuse. Could two
halogens fit on one fuse? Yes but there would not be the 20%
margin there at 9 amps combined. I'd only have 1 amp to spare out
of the 10 amp fuse and that would not be 20%, it would only bwe 10% so
I would go to the next size fuse up and that would be a15 amp fuse for
the two 55 watt halogen lamps I wanted to add. (guess what fuse
Honda uses for your two 55 watt headlamps in the fuse block).
Ok once you get all your loads figured out (and I would only do the
major loads and then add some extra for the little stuff), you can see
you need to feed the loads for power.
Here is what Honda gives you on a stock 1500 alternator:
12v at 35 amps. That is how many watts? 12x35 = 420 watts
In comparason, here is what the Compufire replacement alternator gives
12v at 90 amps. That is 12x90 = 1080 watts.
Before I leave you with your needs, let me say this. It is not
wise to run any electrcal device at it's full capacity for very long.
When I design cirucuts, my loads are 1/2 of the supply and the supply
is 2 times the load. That is my law of halves and doubles for
electronic and electrical design.
that is where my product design reliablilty comes from.
In motorcycles that law is not often able to be practially
applied. So let's say we stay 20% below maximum generating
capacity. That way you can have a failing alternator and still
get by with 20% loss and still work. Another problem with
generating power is that the bike engine is not always turning at
speed to generate what was specified for it at a higher RPM. This
spare 20% helps during
those times as well.
So that means that the stock alt would only be practically useful to
336 watts and the Compufire to 864 watts. Beyond that and you are
on borrowed time so you can see that it pays to engineer your bike
loads in advacnce and live withn that energy budget if you want to be
able to have carefree electrical services on your bike out in the
boonies on a 2000 mile trek.
One more thing... remember when I said there was no free lunch with
energy generation? Guess what, you burn gas for every watt you
create, so larger loads take more gas leaving less power for the engine
and lower MPG as well.
How to make reliable crimp
It always amazes me how many people don't know how to make or test
relaible automotive crimp connections. I see a lot of this in
It is not really the end user's fault because most manfacturers of the
tools or crimp kits with tools don't sell you the right tool.
Nevermind any training.
They want to sell these crimpers that crimp the terminal in the shape
of a pair of parenthesis ( ) instead of an
invasive type in the shape shown in the photos, below.
In the case of the parenthesis crimps, you are lucky to captivate the
in the collapsed diameter tunnel it creates and it is very difficult
to get enough crimping pressure to make a reliable
connection. Plus the wires pull out more easily. One reason
they sell the parenthesis type crimps is
that the metal bands you are crimping have a seam. Parenthesis
crimps don't matter too much where the seam is whereas on the invasion
type crimper the seam position matters a lot more.
Here are some crimp shots with the invasion crimper.
The crimp dies themselves...
Notice in the next picture silouette that the metal crimping band
inside the crimp has a seam. You want that seam as shown,
opposite the invasion point.
The crimp position in the die should be chosen by the diameter of the
crimping band, not the diameter of the plastic insulator around it.
Carefully strip the wire the same length as the crimping band in the
part you will be using and make sure the wire sits inside the
crimping band with all wire strands intact.
If the wire won't fit in, you are using the wrong terminal. If
you want crimp terminals to be reliable you must use the correct
terminal band for the wire being used.
Make a good solid crimp right in the center of the band on the back
side with the wire fully seated.
It is a good idea to be pushing it in firmly as you crimp.
Be sure to test each crimp by firmly pushing in and pulling out the
wire from the terminal. There should be no movement at all.
I don't recommend using stranded wire that has been tinned on the
ends. Rather, use the strands so they can move with the crimping
You can always seal up the ends of the crimping band with dielectric
grease if you are nuts about that type of thing.
The crimpers you buy should have padded handles or your crimps might be
weak as your hand gets sore.
Do it right. It really is the easiest way.
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