In Part 1 of this Series the concept of an accessory electrical circuit was introduced; the idea that electricity flows around a circle from the positive terminal of the battery to the negative one, passing through an accessory or lighting to provide the energy for it to work.

In this Article we develop the idea further, to help you develop a practical grasp of how accessory circuits are created and connected.  We’ll use some examples of individual accessory circuits which are adaptable to various uses and, in the next Article, how they can be combined to form an integrated approach to a safe and reliable accessory wiring system on your GoldWing.

The circuits described in this Article are the building bricks you will need in order to create more and more complex circuits, which will be covered in the next Article in this Series.

Even a simple circuit needs to work reliably and to be safe and that’s essentially what this Article is all about: choosing the correct size of cable, the correct fuse or fuses and where to put them and deciding whether or not you need to use a relay to handle the power involved, as well as a manual operating switch.

In order to work effectively and safely an Accessory Circuit needs:

1. Cable which is thick enough to carry the intended load without overheating.
2. A fuse which is small enough to blow before the cable overheats.
3. An operating switch which can cope reliably with the electrical current it is stopping and starting.
4. And if the operating switch is not big enough to handle the full circuit load itself, you will need to incorporate a relay.

Choosing Cable Sizes

The thicker the cable the higher the load it will carry but the overall thickness of a cable may be misleading; some cables have much thicker insulation that others.  It’s the thickness of the copper core inside the insulation which matters.

There is nothing wrong with using the thinnest cable which will carry the circuit load providing it can carry the load without overheating.  On the other hand choosing a cable which is too thin for the load (or just guessing that it will be OK) is not sensible because that could lead to overheating and even to an electrical fire.

Cable designed for auto-electrical work will often have relatively thin insulation because the voltage in the circuits is low and looms of cables on bikes (and cars) are usually enclosed in a separate outer pvc sheathing to provide any additional physical protection which may be required.  We’ll cover the subject of routing and protecting cable runs for accessory circuits in a later Part of this Series.

The thickness of the conducting core of a cable is quoted these days (in Europe anyway) as a measure of the cross sectional area of the cable in square millimetres (mm²).  Wire Gauge, which used to be dominant, is a measure of diameter which, while useful for single strand wire, doesn’t reflect a cable’s current carrying capacity anything like so accurately.  This is because cables which have lots of fine wires will be able to conduct more electricity than those which have a smaller number of thicker ones.  Confusingly there are also two wire gauge standards: SWG (Standard Wire Gauge) and AWG (American Wire Gauge).  What really matters is the current the cable is designed to cope with and that depends on the thickness of the insulation as well as what’s inside it.  And since current-carrying capacity is usually quoted when cable is offered for sale, that’s the number to go for.

There is no penalty (apart from carrying a little unnecessary weight on your bike) if you use unnecessarily thick cable in a circuit and indeed you will usually need to do so because cable is supplied in only a limited number of sizes.  You will, more often than not, need to round up the current capacity you choose to the next higher current capacity which is actually available.

It also OK to use a mixture of cable sizes in the same circuit as long as long as the thinnest cable in the circuit is up to the job of carrying the circuit load and providing you fuse the circuit accordingly.  In practice you will often need to do this.  For example LED display lighting units are often supplied with short leads made of extremely thin cable and even if you use the smallest size of automotive cable (you may find some which is rated at 8 amps) to feed power close enough to connect to it, there will still be a mismatch of cable sizes. Likewise the cable tails which are supplied with in line blade fuse holders are rated at either 20 or 30 amps, yet you will often use them with much smaller fuses and thinner cable in your circuit.

The current carrying capacities quoted in the following table are for the selection of thin walled low voltage automotive cable supplied by Kojaycat. This Company supplies cut lengths as well as whole reels in a wide variety of colours and therefore covers everything you are likely to need.  Current capacity for cables from other sources may vary slightly.

Capacity (amps)	Size (mm2)
11	0.5
16.5	1.0
25	2.0
33	3.0
39	4.0

Much larger size cables are used for your bike’s main battery leads because they have to cope with the high current draw of the starter motor, but the cables in this table will provide a range of capacities which is more than enough for even the most demanding of accessory circuits.

Interestingly Halfords quotes significantly lower current ratings for their cables of equivalent cross sectional area as follows:

Capacity (amps)	Size (mm2)
5	0.65
8	1.0
17	2.0
27	not stated

This difference in rating may reflect the thickness of the insulation (thicker insulation reduces a cable’s current capacity) or it may be that Halfords is being extra-cautious, or a bit of both.  Halfords supplies cable in small reels of between 2.5 and 7 meters; the thicker the cable the less you get on a reel.

Wiring Colour Code

Honda uses conventional wiring colours (called a Wiring Code) across its vehicle range; for example green cables are always ground connections.

There aren’t enough colours for all the different applications and so combinations of colours are also used, for example brown with a white stripe or white with a brown stripe, and this increases the available permutations considerably.  The particular colour of cable used for each cable run and circuit on the bike is shown on the wiring diagram in the Service Manual and this can be very helpful when you are troubleshooting.

Honda doesn’t publish it’s Wiring Code but a list of some of the colours they use, which you might find useful if you haven’t got a wiring diagram or if you want to install compatible cable colours for your accessory or repair wiring is available on the internet, for example by Clicking Here.

Looming cables together can affect the cable size you need

A cable’s current-carrying capacity varies with temperature and so strictly speaking if you intend to gather your cables together in looms (so they will warm each other up and lose heat less quickly) you might need a thicker cable than the nominal circuit lead would imply.  The designers of your GoldWing circuits will take this sort of thing into account in considerable detail but thankfully as long as you are not running your cables at their full rated capacity and looming them up with lots of other cables, you are unlikely to need to worry about this.

Fuses

In order to prevent overheating of cables in the event of a short circuit all accessory circuits need to have a fuse incorporated into them, sometimes more than one.

A fuse is a short length of electrical conductor which will self-destruct safely (i.e. it will “blow”) if the current flowing through it exceeds the design limit. When a fuse “blows” it disconnects the circuit and prevents further damage.

Fuses of various types are available but for GoldWings only two need be considered:

1                    Automotive “blade” fuses consisting of two connector blades held together by a plastic bridge inside which is the fuse itself, a zig-zag piece of wire.

2                    A glass tube fuse which has a length of thin fusible wire inside with a metal cap either end.

Blade fuses are now the industry standard in auto-electrics and they are used by Honda in the manufacture of your GoldWing.  All GoldWings have these plastic-covered “blade” fuses, differing only in physical dimensions; the GL1800 has more compact “mini” fuses than earlier models.

On the photo of a GL1800 fuse box which heads this Article you can see the rows of coloured plastic fuse heads.  The lid of the fuse box is labelled with what they all do.  Note that there are differences between some model years of GL1800 and if you ever need to replace the fuse box lid you need to be sure to get the correct one.  The “A8” top right on this fuse box lid indicates the model year.

The colour of a blade fuse indicates the fuse’s rating, i.e. the maximum current it will tolerate before blowing. The number of amps is also printed on it.

The fuse itself is the zigzag of wire inside the plastic bridge section which connects the two blades. The plastic is transparent, which allows you to see whether the fuse is intact.  If you can’t see the zigzag the fuse has blown. Blade fuses are all the same shape and physical size so they are potentially interchangeable – which is why you should always double check before replacing a blown fuse.  Never replace a blown fuse with a bigger one unless you really know what you are doing.

The fuses which Honda design into your GoldWing’s electrics are arranged on a fuseboard. This is a sensible way to arrange things when a substantial number of fuses are required, as of course is the case on a complex bike like a GoldWing.  The fuses are all in one place and they can be identified easily from the diagram on the lid if you need to check any of them when you are trying to diagnose a fault.

A similar approach can be taken with accessory circuits if you wish.  A specially designed supplementary fuse board is available from Electrical Connections for both the GL1800 and GL1500, to be installed near the Battery.  They provide fuse protection for up to six accessory circuits.  While is a neat way of providing fuses for accessory circuits and they ensure that the fuses are where they should be, as close as possible to the battery, they may not provide a complete solution to your accessory needs, especially if you wish to incorporate relays into your circuits.  Some accessories may need in line fuses anyway.

The alternative to a supplementary fuse board is to use in-line fuse holders for all your accessory circuits.  These are available for the same type of blade fuse which your GoldWing uses and there are both open fuse holders (allowing to see the fuse in place) and a splash-proof version, which are a better choice for a bike.

There are practical advantages (eg for carrying spare fuses) in sticking to the same type of fuse as the bike for your accessory circuits whenever you can.  But some accessories, such as satellite navigator receivers and speed camera detectors, may be supplied with their own built-in or in-line fuses, in which case of course you should normally make use of those.  They will often be tubular glass fuses rather than the blade type.

Although there are various sizes and types of glass tube or “cartridge” fuse available, for auto-electrical and car radio circuits a 1¼ inch by ¼ inch glass fuse is the norm and in-line fuse holders are readily available for them.  The fuses are available for capacities of 10 amps or more but for accessory circuits on a GoldWing you would normally use glass tube fuses in capacities of 2 amps or less.

In line fuse holders are usually supplied with short lengths of cable already attached and so the current rating of these cable tails can be a limiting factor.

For example the in line blade fuse holders supplied by CPC come in two different ratings, 20 amps and 30 amps.  If you plan to use a 30 amp fuse, for example in the cable connecting the positive side of the battery to a group of relays, you will need to make sure you have the right one.

In line fuse holders for glass tube fuses are designed for currents of 5 amps or less so don’t assume the cable tails are rated for any more than that.

A very simple accessory circuit

Let’s take the example of the installation of a pair of amber passenger footboard under-lights on a GL1800 to illustrate a very simple accessory circuit.

If you are content for these lights to be on all the time your bike is running, as your headlights and tail lights are on all recent GoldWings, you can install them without an operating switch, which makes life considerably easier.  Instead they can be controlled by using the bike’s Accessory Terminals, which are  whlive when the ignition is on (or switched to “Acc” but not otherwise.  By connecting the floorboard under-lights’ power leads directly to these Terminals they will come on and go off with the bike’s running lights.

These accessory lights are supplied with power leads which are long enough to reach the Accessory Terminals, so potentially you could simple connect the red and black power leads from both lights directly to the bike’s positive and negative Accessory Terminals respectively, simple as that.

You will have to take the bike’s seat off to route the power leads from the right hand footboard to the Accessory Terminals so potentially their installation couldn’t be simpler.  Each light will be connected by its own accessory circuit, i.e. its own power leads and nothing else.  The bike’s Accessory Terminals are protected by their own 5 amp fuse on the main fuseboard, so that’s all there is to it – or is it?

Not so fast.  Even if nothing else is connected to the Accessory Terminals (and the whole 5 amps is therefore available to them) you need to consider the load on the bike’s Accessory Socket under the left glovebox, since this is also protected by the bike’s 5 amp Accessory Fuse.  If you have, for example, an MP3 player in the glovebox which is powered from that socket, you need to add up the total load of what will be three accessory circuits (your MP3 player plus the two footboard lights) protected by a single 5 amp fuse.

In this particular example there is unlikely to be a problem of circuit overload because an MP3 player is likely to draw less than one amp and the floorboard lights will probably only draw about 0.5 amps each, so the combined load on the bike’s Accessory Fuse will be two or at most three amps.  So unless there are other accessories also connected to either the Accessory Terminals or the Accessory Socket, the bike’s Accessory Fuse is unlikely to blow.  End of problem – or is it?

Not quite.  The power leads supplied with the two footboard lights are really quite thin.  The lights they supply only draw 0.5 amps so are these cables capable of carrying the 5 amps  which the Accessory Fuse will allow to flow?  Does it matter if they aren’t?

Worst case scenario is for a short circuit to occur in one of the lights or in a power lead near the footboard, so that uncontrolled flow of electricity takes place unless and until the 5 amp Accessory Fuse blows, which of course it will if there is a short, fairly quickly too.   But will the thin cable of the power lead suffer heat damage by carrying up to 5 amps before this 5 amp fuse blows, which would damage the insulation around it and require the cable to be replaced?

The answer is no because the power leads supplied with these lights probably are capable of coping with 5 amps for the very short time before the bike’s Accessory Fuse blows.  But if the bike’s Accessory Fuse had been replaced by a higher capacity one, say 10 or 20 amps, for example because the 5 amp had blown and a spare wasn’t available, then it would be a different story; the footboard light power leads would seriously overheat and could well catch fire – under the seat and close to the fuel tank.

Ideally therefore, even if the correct 5 amp fuse is in place to protect the bike’s Accessory Terminals, the power leads for the pair of passenger footboard under-lights should have their own in-line fuse installed, rated just above the current they will draw.  Since each of the floorboard lights is connected by its own power leads, and therefore its own accessory circuit, each should have a 1 amp in-line fuse incorporated close to their connection with the positive Accessory Terminal.

A professional auto-electrician would probably regard installing separate 1 amp in line fuses on each power lead of these small lights, although ideal, as a bit OTT.  Relying entirely on the 5 amp Accessory Fuse, so connecting the power leads directly to the positive Accessory Terminal, is not unreasonable.  What I did on my own bike was a compromise;  I connected the red cables from both footboard lights (together with the red cables from two LED Opera Light Bars which I was also installing at the same time) to a single 2 amp in line fuse, the other end of which I connected  to the positive Accessory Terminal. This way if a short occurs in any of these four light circuits their shared 2 amp fuse will blow instead of the 5 amp Accessory Fuse – and I won’t lose power to my satellite navigator, which is powered from the bike’s Accessory Socket.

The final consideration in the installation of the pair of floorboard under-lights is the protection of their thin, and therefore vulnerable, power leads as they are routed from the underside of the footboards, around the footboard hinges, past the hard edges of  the frame covers, up along the frame and across the space under the seat towards the Accessory Terminals.  We’ll deal with routing and protecting cable runs in a later Article but for now let’s just note that these thin power leads will need protecting, by sheathing and/or securing with cable ties.

Incorporating an Operating Switch

On my own bike I wanted to be able to switch off the amber footboard and opera lights when I was using display lighting of other colours, so the amber wouldn’t conflict.  I have also contrived to be able to switch off all white a red lighting for the same purpose too, but that’s another story for later.  For now let’s concentrate on the pair of footboard under-lights again, with or without Opera Lights and incorporating an operating switch.

Switches of various types are available and can be located in various places, as explained in Part 2 of this Series.  On my bike, on the right hand side of the handlebars on top of the brake master cylinder, I already had a row of three switches.  These were all in use but I managed to re-allocate one of the jobs they were doing and so free up one switch for use controlling my group of four amber Opera and foorboard underlights.

As supplied these switch pods have four cables one of which (very sensibly it’s the red one) is intended for connection to a positive 12 volt supply which is shared internally by all three switches, so that when each switch is closed, it connects this 12 volt supply to that switch’s own output cables.   So there are a total of four cables in the switch pod loom, one red and three other colours.

I had already carefully routed this loom of four cables (inside the pvc sheath which they come with) along the handlebar and then around the steering head and into space below the right hand glovebox where I connected each of them to another cable (i.e. I extended them all) to allow all four to be routed underneath the top shelter to the space under the seat.  More about how to do this later, for now let’s just assume that your switch cables are available under the bike’s seat, which is also where the power leads from the amber lights are too.

The red cable in the switch set of four, the shared 12 volt input for the switches, needs to be connected, via an in line fuse, to the bike’s positive Accessory Terminal.  A power supply of up to 5 amps, less whatever is also drawing power from these Terminals and the Accessory Socket, is now available through each of the three switches.

(There are other ways of connecting the switch pod’s red input cable to 12 volt supply in order to ease this constraint on 5 amps maximum, but remember that these are small switches, therefore of small capacity and they cannot be expected to handle large currents, such as those drawn by fog lamps.  Their capacity isn’t stated but they shouldn’t be expected to handle more than 5 amps each at most and I don’t like to put more than 2 amps through them.)

While you cannot safely connect high power accessories like fog lights this way, a pair of amber passenger footplate under-lights, even if you also add two Opera lights, is perfectly OK because the total current draw of all four lights will be less than 2 amps.  This simple arrangement of connecting one side of the operating switch to the positive Accessory Terminal is, providing there isn’t more than 5 amps in total being drawn from the bike’s Accessory Terminals and Socket, perfectly adequate.  The cables to and from the switches are good for at least 5 amps and the bike’s Accessory Fuse will prevent that total load on all three switches being exceeding 5 amps.

The output cable from the chosen switch, which has also been routed to the space under the seat, can therefore be connected to the red cables of the amber lights, i.e. the two power leads of the passenger footboard lights and the Opera Lights. Ideally this connection is made through and in-line fuseholder and a 2 amp fuse is inserted.  This will prevent  a short in any of the amber lights causing loss of power to whatever the other two switches are operating.)

To complete this accessory circuit, the black cables of the power leads need to be connected either to the negative Accessory Terminal or by some other means directly or indirectly to the battery’s negative terminal.  Instead of having four cables all connected to the bike’s negative Accessory Terminal it will be better to contrive a Common Ground Connection under the seat to which all your accessory circuit returns can be connected.  More about how to do that that later.

More power needed?  Incorporate a Relay

So now let’s consider an accessory circuit which can allow more current to be drawn, for example to power a pair of fog lights.

Small lights like the two passenger footboard under-lights we’ve been considering (and also LED display lighting) consume a relatively low levels of electrical power and so they can safely be connected in the way described above.  And if appropriately sized fuses are incorporated into the individual accessory circuits, failure of one circuit will not cause them all to lose power.

However accessories or combinations of accessories which draw more than 5 amps call for a different approach.  Power can still be drawn from the bike’s Accessory Terminals to control the more power-demanding accessory circuit but the circuit’s operating power must be connected to the bike’s Battery using a relay.

The essence of what a relay is and does was explained in Part 1 of this Series but it will bear repeating here. Relays are electrically controlled switches which can handle much higher currents (30 or 40 amps if necessary) than the small manual switches we install on our GoldWing’s handlebars which can handle a maximum of 5 amps. They use a very small electrical current (between 0.1 and 0.2 amps) which operates a solenoid which in turn closes the large electrical contacts which can safely handle the bigger current.

Relays therefore have four terminals, two for the controlling circuit (to operate the solenoid) and two for the power circuit, which connect the bike’s Battery to the accessory.  The relays used for autoelectrical work are small black boxes with 6.3 mm wide blade terminals.  They take push-on female connectors which are available in red, blue and yellow size crimp terminals; these were covered in Part 2.  (Changeover relays have five terminals but we’re ignoring those for now.)

For all practical purposes relays are merely black boxes with four (or five) blade terminals.  All you have to do is make the correct connection.  Fortunately the blades on relays are numbered and they often have a helpful little diagram printed on one side to remind you what they do.

Terminal Number	Connect to
30	Power Input (Battery positive, via fuse)
87	Accessory Load
85	Ground (Battery negative, energising circuit return)
86	Operating switch (Energising 12 v feed)

So for purposes of installing our pair of fog lights we can still use a small switch such as we used for the passenger footboard under-lights.  But instead of connecting the switch’s output directly to the accessory we connect it to Terminal 86 of a relay.

In order for the relay to operate Terminal 85 must be connected to ground, i.e.directly or indirectly to the negative side of the Battery.  In practice, since we drew power for the operating switch from the positive Accessory Terminal we might as well connect to the negative Accessory Terminal.  (In general it is best to avoid connecting directly to the Battery’s negative terminal, not least to avoid clutter.)

Next we connect Terminal 30 of the relay to the power source which, when activated, it will connect to the fog lamps.  The power source has to be, because the bike’s Accessory Terminals can’t supply enough power for this task, the positive terminal of the bike’s Battery.  (If you have installed a supplementary fuseboard you can use that, but for the moment we’re assuming you haven’t.)

In Part 1 of this Series we calculated that the fog lamps will draw about 6 amps from the Battery but more, 7 or even 8 amps, when the bike’s engine is running and therefore there will be 14.3 volts rather than just 12 volts applied.  So for the power lead to the fog lamps we need a cable which can handle at least 8 amps with an in line fuse to match.

Automotive cable rated at 8 amps is available and so is a 7.5 amp blade fuse, so we could use those, just.  But that leaves little or no margin and I would be happier using cable rated at 10 amps or more which would allow the use of a 10 amp fuse.  Kojaycat’s smallest (0.5mm²) cable is rated at 11 amps, so that will do nicely and will allow the use of a 10 amp fuse.  The in line fuse holder should be at the Battery end and the cable is connected (assuming for now that only one relay is being installed) directly to the Battery’s positive terminal.

Next we connect the relay’s power output terminal, Terminal 87, to the fog lamps.  For this we must use cable which can handle at least what the power supply fuse will allow, so a minimum of 10 amps.  We could use a single core cable for this job but thinking ahead to the next task, providing a return connection from the fog lamps, it will be expedient to use twin core cable.  Assuming we choose twin core cable (of at least 10 amp capacity) it will probably turn out to have one red and one black cable inside it’s outer sheath.  Connect the red cable to Terminal 87 of the relay and route the cable to one of the fog lamps.  (More about routing cables around a GoldWing in a later Article in this series, for now let’s assume that’s it’s done.

Both fog lamps need to be connected to the relay, so as the red cable is being connected to the first fog lamp it reaches and additional length of the same red core of the same twin core cable (long enough to reach the second fog lamp) is connected as well.  (This is done by using a blue rather than a red crimp terminal connector; blue size crimps will accept two red-size cables at once.)  The second length of power cable is then routed to the second fog lamp where its red core is connected to the fog lamp in the same way as the first.

Finally, to complete the accessory power circuit, we need to connect the other terminal of each fog lamp to the battery’s negative terminal, i.e. “to ground”.   We say “to ground” because the negative terminal of the Battery on a bike is always connected electrically to the bike’s frame and engine block, an accessory circuit can if necessary be completed by connecting to the bike’s frame or engine.  Indeed for some accessory circuits it is better to connect the accessory’s return cable to the bikes frame rather than directly to the battery because it can help to reduce audio interference on the bike.

So in the case of fog lamps, which are installed low down in front of the engine, we could have chosen to use single core cable to connect the relay to the fog lamps and then more single core cable to connect the fog lamps’ other terminals to ground somewhere nearby, thereby saving on cable.

But Honda doesn’t often do this in its circuit design, preferring to incorporate a return cable run back to some central grounding point.  We’ll go into this idea of a central grounding point (rather than connecting directly tot he battery’s negative terminal, in the next Article.  For now let’s just say that we should use a return cable from our fog lights back to the part of the bike where the relay is installed, where it will then be connected, albeit indirectly, to the negative side of the battery.

Power Circuit without an Operating Switch

The final simple circuit we need to consider to complete our repertoire of circuit types is a power circuit (i.e. a circuit capable of taking more load than the bike’s Accessory Circuit can cope with) which does not need its own operating switch, yet which is better to be “live” only when the bike is running, for example a power lead for heated clothing.

Your heated garment may have been supplied with its own built-in heat controller or switch and a dedicated power lead, intended for direct connection to the bike’s battery and incorporating its own in-line fuse.  That will work safely enough but the power lead will always be “live” when the bike is parked up and this might be undesirable if it has to be left dangling.

If the total current draw of your garment is no more tan 5 amps and you have nothing else connected to either the bike’s Accessory Terminals or the associated Accessory Socket, connecting the garment’s power lead directly to the Accessory Terminals will suffice.

In reality however your Accessory Terminals and/or Socket are likely to be needed for other things too, so it will be better to create an accessory circuit specially for the heated clothing.  You can do this by using power from the Accessory Terminals to energise a relay and using that to supply power to the garment’s power lead(s) – the advantage being that you won’t be restricted to 5 amps, so you can connect more or warmer garments if you wish.   (Any fool can be uncomfortable.  I have been known to wear a combination of heated socks, a heated waistcoat and heated gloves; I was roundly mocked for doing this as I met up with some other riders, including sports bike riders, for a winter ride.  Two hours later at the coffee stop I was mocking them and offering to share body heat, such was the contrast between my cosy comfort and their frozen agony.)

This circuit is identical to the fog lamp circuit described above except that the power supply to Terminal 86 of the relay is taken directly from the positive Accessory Terminal rather than via a switch.  This way the relay will be energised whenever the Accessory Terminal is live, so whenever the ignition key is turned on or to the “Acc” position.  Cable size isn’t an issue for the relay’s energising circuit and you can use the smallest cable you have to hand.  But ideally you would incorporate an in-line fuse because energising the relay will draw less than 0.2 amps, so a fuse rated at 0.5 amps would be better than relying on the bike’s 5 amp Accessory Fuse.

Next Article

Part 5 of this Series will cover branching accessory circuits, such as those for multiple LED display lighting units, and safe ways of operating and supplying power to multiple accessory circuits, which GoldWing owners often wish to do.