Wiring Loom Routing

tstewart
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Wiring Loom Routing

Postby tstewart » Thu Mar 08, 2018 6:38 pm

Got the wiring loom today for my Arrow.

Can anyone tell me how the wiring is routed to the headlamp, points and the alternator?

Thanks
1952 Ariel NH350, 1960 Ariel Arrow, 1955 Francis Barnet Falcon 197cc, 1954 Norton Dominator.

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Roger James
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Re: Wiring Loom Routing

Postby Roger James » Fri Mar 09, 2018 7:46 am

Hi,
The main body of the wiring loom runs down the outside of the frame within the dummy tank on the offside, at the front end it comes up out of the front of the dummy tank where there is a good gap and you push it through the large hole in the back of the headlamp in order to connect up to the ignition/lighting switches and, ammeter, sometimes also you might have a feed to illuminate the speedo, the bulb holder usually clips onto the speedo bracket, there are other wiring connections in there also for the dip switch cable run from the switch on the handlebars and one for connecting up the horn wire and three for the headlamp bulb and side light.
At the rear of the main wiring harness towards the back of the dummy tank where it sits on top of the frame you will see a little slot cut into the dummy tank, the wiring harness runs through that slot resting on the top of the frame, there are not many wires left at this point so although the slot is very small its enough for the thickness of the cable, this end of the harness has your wiring feeds for the battery, and connections for two sub harnesses these are extra to the main harness and you might have to make them up unless you are lucky and have them, one sub harness passes through a hole in top of the tail section and down inside the short rear inner mudguard where there are clips to hold it in place, you connect the two ends to the rear brake light switch. The other sub harness goes through the same hole in the tale section (protected by a rubber grommet) and runs on the underside of the tail section again held in place by clips welded to it and connects up to the rear light.
With regard to the Alternator wiring, the harness containing three wires from the Alternator run up alongside the speedo cable (originally in a plastic cable sleeve but these are sometimes discarded these days as its fiddly to get all the cables running through it by the time you've added the sub harness from the points and the horn wires) the alternator wires come out of the top of the sleeve that ends inside the dummy tank and connect up to the wires from the main harness. I usually find insufficient length to do this, some wiring from alternators are a bit on the short side so I make up a short harness of my own to give a bit of slack in the harness. You will find the benefit of this the first time you need to remove the alternator for whatever reason and can pull the cable through the slot to remove the wires from the bullet connectors, far better than messing about down the side of the frame inside the dummy tank especially when re connecting them.
I've mentioned the points sub harness, back in the day Ariel routed it down from the points towards the footrest then under the primary chaincase then up past the carb to the offside where it is then routed up through the sleeve into the dummy tank to connect up to the wiring from coils etc but many take the route used on the Leader straight up and across the back of the cylinder heads through one of the H.T. holes to be connected up down inside the frame where the coils are mounted.
There is just one more thing to mention, branching off from the main section of harness in the dummy tank you will find three wires, two white and one Black/White these are threaded through a hole in the frame on the offside, put your hand down the side of the frame to feel for the hole as you cannot see it with the dummy tank in place, these wires are for connecting up to the wiring from the coils, there are also the wiring from the Rectifier that is bolted to the nearside of the frame within the dummy tank to be connected, the wiring from the rectifier runs across the top of the frame to the hole where you put your hands through to fit the coils, Its not easy sometimes connecting all these wires up working through that hole, best to refer to the manual wiring diagram when you are doing this.
Hope the above doesn't make it sound complicated as it isnt, just a bit fiddly connecting up some of the wiring down inside the frame.
If after connecting up all of the harness and you connect up a battery but the lights dont work, it could be that you have no earthing because someone has done a good job of painting the dummy tank and headlight stopping the earthing, sometimes you can rock the headlamp and this will wear the paint away around the headlamp mounting bolts getting it to earth or if you dont want to do that and save the paint you might have to run an earth wire from the headlamp to the frame, there is a connection on the main headlamp bulb holder for a earth wire.
Jess
Last edited by Roger James on Fri Mar 09, 2018 9:15 am, edited 2 times in total.

tstewart
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Re: Wiring Loom Routing

Postby tstewart » Fri Mar 09, 2018 9:08 am

Thanks that's a great explanation, I had made a few incorrect assumptions. I am grateful for the time and trouble taken to answer my question.
1952 Ariel NH350, 1960 Ariel Arrow, 1955 Francis Barnet Falcon 197cc, 1954 Norton Dominator.

iansoady
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Re: Wiring Loom Routing

Postby iansoady » Fri Mar 09, 2018 10:50 am

I always add separate earth wires on all my bikes as especially when bits have been painted /powder coated the standard earthing is suspect.

That description from Roger is superb.
Ian
1952 Norton ES2
1982 Moto Guzzi V50


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