93 K1100LT
I find wiring diagrams very challenging along with most electronic stuff
I am fitting a sidecar on the above bike
To this end I want fit another fuse box in the sidecar to run an auxiliary fuel pump and USB charging port etc
The power for the fuel pump will be put through a relay (advice from a friend)
Does anyone see an issue if the source for the power to the sidecar is taken out of the Ignition switch plug under the bike tank,(the big orange plug). I have selected the green wire
Please advise if this is not a good idea or feel free to provide alternative solution as long as they are simple and easy to follow

A couple of questions for you Packo, just to set the scene.

(1) Do you want the auxiliary fuel pump to run when you have the ignition switched on?

(2) How are you going to control the fuel pump? e.g. by manual switch, or by some level device, or maybe when the low fuel warning comes on for the bike tank.

(3) Do you want the USB charging facility to be available when the ignition is off?

I personally would not want to put any more electrical load through the ignition switch so would not tap into that green wire.

PM sent.

Cheers

You would be ill advised to draw your additional power through the ignition switch. The best configuration for an additional fuse box would be to get one that has a relay to cut off the power source. These usually have three inputs - one large one for a positive feed from the battery through a large gauge wire, another large one for the ground return, and a third smaller connection that would control the relay. That control wire could go to the ignition switch as you envision. The current drawn by your fused accessories on the sidecar will go through the large gauge wires and will be enabled by the control wire when you switch on the ignition.

I would that the relay be controled by the loadshed relay to prevent unnecessary power usage during starting.

I assume you don't want the aux fuel pump running all of the time.  For a manual switch what I would do is install a BMW switch in one of the four switch slots up by the "dome light" on the K1100LT.  I'd power that from the round white alarm connector in the relay box (the green/brown wire is switched power through fuse 7) and then through the switch have it power the fuel pump relay 85 terminal to turn the fuel pump on.  Getting the fuel pump switch power from a switched source ensures the fuel pump can't run when the bike is turned off.

For power to the fuel pump relay I'd run power from the plus terminal on the battery to the fuel pump relay.  It might be best just to use an inline fuse close to the battery on that.  

You need to now how many amps the fuel pump is to figure out the minimum gauge wiring to use.

hi packo

can I also make some suggestions

you will likely have other electrical items attached to the sidecar , running lamps , turn indicator , brake lamps , etc

could I suggest to use a 7 or 8 pin trailer type plug and socket  as it leaves the bike  so that it can be quickly disconnected in case of any catastrophe

I would imagine that there would be a few control cables involved with what you are anticipating fitting to the sidecar  and the contacts on the trailer plug are sufficiently rated  for the jobs that you are going to do .

suggestion 2

run a cable from the starter relay - battery side connection through a suitable fuse holder for a total current of 20 amps to a relay as suggested above
control that relay from the switched power on the bike  so that the relay is active only when the bike is keyed on , from this you could run accessories like the usb adaptor and other things as it comes out of the controlled relay ,
but also double up the feed input of that relay , to provide a feed of power - always active to the sidecar , possibly a cigarette lighter socket  in the sidecar for powering up a phone charger etc  ,that can then be disconnected - or used only when necessary. but always active and already fused from the battery supply .
 don't forget that the usb adaptor will draw current when not used , (small amounts ) but still a drain all the time unless switched active with the bike electrics .

take these output cables through the trailer plug  along with other cables required for the running lighting etc

the advantage of doing this will be in the loom that be formed with all these cables , can be wrapped in a protective sheath , or trailer wire , already double insulated and all neat and tidy with good termination points at the plug- socket .

suggestion 3

make a wiring colour code placard , perhaps on carboard then heat wrapped - sealed and mounted in the side car , and inside the electrics box for a second copy so you remember what colour wire does what , further down the road

also as suggested, switching the accessory pump via a switch on the dash pad to another relay in the electrics box then feeding off to the trailer plug

suggestion 4
and don't forget a damn good earth cable of about 20 amps , doubled up on the gearbox connection point  as the return wire for all those bits and bobs is a pretty wise idea . (once in the sidecar end of things a small brass bus bar screw terminal block can connect all the earth points at one location )
something like this perhaps ?


good luck

Thanks for the replies and suggestions, much appreciated. With them in hand and a phone discussion with Gaz I now have a plan that I can implement with much more confidence

I build the wiring looms for a well-known UK sidecar company (naming no names, because their range is undergoing a complete redesign). This is the diagram, if it helps:



For the fusebox I use one of these:-

https://www.ebay.co.uk/itm/12V-24V-4-WAY-BLADE-FUSE-BOX-HOLDER-BUS-BAR-WITH-LED-FAILURE-WARNING-LIGHTS/122447683928?hash=item1c82736158:g:GMQAAOSw3utY8Zuo

It makes identifying blown fuses easier. There's also room next to the common power feed to drill a hole and use a small bolt for a common earth point. The relays are made by Durite or any similar well-known brand as I can't afford to have a high failure rate using cheap no-name Chinese stuff. I mount the relays and fusebox on an aluminium plate which itself is mounted on three 20mm standoffs. This allows room for the wiring to run underneath the plate but you'll need to provide cutwaways to bring the wires up the the fuses and relays. The relays are mounted in sockets with the wiring side towards the short box wall. This gives room to wriggle them out if they need replacing. Similarly, the fusebox goes up against the other short wall.

The entire assembly is mounted in the boot/trunk in a water-resistant (IP65) box with a transparent lid and the cables fed through tight grommets. The box is made by Geros (Italy), part number GR17208:-

http://www.directindustry.com/prod/geros/product-54049-971519.html

The standoffs are mounted to the box through the board mounting screw bosses (you can see them in the picture about 15mm in from the outside edges) - I drill the bosses through to the outside world and then countersink to use 5mm stainless countersunk screws. To keep the watertight integrity and to make it possible to remove the mounting plate without inadvertently unscrewing the standoffs, the drilled hole is 4.5mm and I allow the screws to cut their own way through. The standoffs are screwd down with a bit of Loctite on the threads.

Yes, I know; a picture would have been really helpful but I'm not due to make any more for a couple of months yet. Apologies for that . If you're interested, I can get the company owner to photograph the prototype as I know that's still floating around the shop.

I build the wiring looms for a well-known UK sidecar company (naming no names, because their range is undergoing a complete redesign).


Dai,
 Thanks very much for the reply and the explanation of your sidecar loom. I have chosen the exact same fusebox as you use except that I have  a sixway instead of the four. I like the idea of the alum mounting plate and the use of the Junction box with a transparent lid.
You are right it would have been good to have a photo but I think I understand it reasonably well from your description, and should be able to put something very similar together