The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: AdrianJ on 26.06. 2019 11:08

Title: Wiring Loom Layout
Post by: AdrianJ on 26.06. 2019 11:08
I'm just fitting a new wiring loom to the plunger A10.
I didn't keep proper records when I took the old one off - though much of it was just a bunch of wires - all colour coded black!
A couple of questions:
Should the regulator connection strip be at the front  or the back? (i'm having difficulty arranging the nest of wiring which will be under the saddle).
Does the main loom run under the top frame tube or between the tube and the tank?
Any help gratefully appreciated.
Adrian
Title: Re: Wiring Loom Layout
Post by: Greybeard on 26.06. 2019 11:31
On mine: The regulator connections face to the front of the bike. The loom is under the frame top tube. I used cable ties to hold it in place. I was pleased to see the new loom I bought had earth return wires in it so I didn't need to rely on dodgy returns via the head bearings and the frame. Have you got the extension piece to go to the dipper switch?
Title: Re: Wiring Loom Layout
Post by: AdrianJ on 26.06. 2019 13:52
Thanks Greybeard,
Just what I needed to know.
Yes - I've got the dip switch part and an earth running to the headlight area. Where did you attach it?
It's one of the modern "Lucas" looms.
Regards,
Adrian
Title: Re: Wiring Loom Layout
Post by: Greybeard on 26.06. 2019 14:40
.. earth running to the headlight area. Where did you attach it?

For Earth, maybe we should say Ground or Return.
It was a while ago! Without taking the headlamp apart: I think the Return goes on one of the light switch terminals. Although having Returns in the loom should mean the frame doesn't need to be part of the electric system I attached the loom Returns to the frame bolt under the saddle.
Title: Re: Wiring Loom Layout
Post by: AdrianJ on 26.06. 2019 21:37
Yep! That's where I'm connecting them. Though it's taking a lot of sanding to get a good contact.
Checking with a multimeter and
I get 7 or 8 ohms between there and other adjacent frame points.
The headlight is OK with the return wire, but Istill need a frame connection for the rear and (I think) the dynamo.
Just need to establish a good connection.
As an old school electrical engineer, I'm happier with earth than ground, though in the case of this bike return makes more sense.
Adrian.
Title: Re: Wiring Loom Layout
Post by: Greybeard on 26.06. 2019 21:48
Ah yes, the dynamo uses the bike frame doesn't it.
Title: Re: Wiring Loom Layout
Post by: Greybeard on 26.06. 2019 23:04
I think my loom has a return for the rear lamp
Title: Re: Wiring Loom Layout
Post by: AdrianJ on 26.06. 2019 23:07
That's a good idea, but mine doesn't. Just headlamp assembly.
Thinking about it the dip switch and horn also have to use the frame.
Adrian
Title: Re: Wiring Loom Layout
Post by: Billybream on 27.06. 2019 04:53
Are you adding fuses during your rewire, very worthwhile protection.
Title: Re: Wiring Loom Layout
Post by: AdrianJ on 27.06. 2019 08:03
Yes, but just the one. 25A in the return to the battery.
Title: Re: Wiring Loom Layout
Post by: Greybeard on 27.06. 2019 08:22
I put a double fuse box in the battery feed cable. It's mounted on a small stainless steel bracket attached by one of the regulator box studs. I think they are 16 Amp fuses. You can also see my waterproof battery connector just below the fuse box. This is a 13AH battery and rubber case, (from Paul Goff). There is very little room between the battery top and the case lid so I've soldered wires onto the battery tags and have a connector, as shown.
Title: Re: Wiring Loom Layout
Post by: Swarfcut on 27.06. 2019 09:11
Adrian, 25A is a bit heavy a fuse. 10amp will just about cover a full load, 15amp allows a bit of margin. 25amp  and the wiring stands a better chance of frying before the fuse blows. I used one of the battery carrier studs as a central earth point and like GB, added an extra return from the rear light assembly, as getting a good rear mudguard/frame electrical connection is always awkward especially with powder coated and  painted parts, seems a pity to go scraping off newly finished items.


 Swarfy.
Title: Re: Wiring Loom Layout
Post by: Greybeard on 27.06. 2019 09:21
Thinking about it the dip switch and horn also have to use the frame.

Dipswitch no, not on mine anyway. There was a short piece of loom to go from the headlamp to the dipswitch.

The Horn on my loom has a return wire. You can see the wires coming up from the horn in the first picture above. There is also an alternative horn connector spur beneath the petrol tank.
Title: Re: Wiring Loom Layout
Post by: AdrianJ on 27.06. 2019 10:35
You are correct - there's no return on the dipswitch just the two live leads to the bulb and the supply.
I can easily change the fuse. I thought 35W for headlight  - 15 + 10 for rear and brake + 15 + 10 for lights on chair = 85W
This should be about 14A which I approximately doubled as a safety margin. I've probably overestimated.
I have two 6V batteries in parallel in a rubber case with plenty of room for the fuse holder as well.
Adrian
Title: Re: Wiring Loom Layout
Post by: Greybeard on 27.06. 2019 13:13
I've just been working on the mag kill button. That has its own wire to the mag and just earth's to the handlebar.
Title: Re: Wiring Loom Layout
Post by: duTch on 27.06. 2019 14:36

 AJ- I'm no expert, but I think when running two batteries in parallel is a good idea to have some kind of doodads (diodes) between them to stop the potentially weaker one draining the potentially strong one.... *dunno* ...?  (I'm doing it at the moment, but have a manual switch for one or the other-not ideal either)
Title: Re: Wiring Loom Layout
Post by: AdrianJ on 27.06. 2019 14:43
I was surprised that it wasn't part of the loom, but there's nothing wrong with my old one.
Hoping to get the wiring finished today or tomorrow - then cure the primary chain case leak :-) and fit tank, saddle and sidecar.
I'll post some photos when it's finished
Adrian
Title: Re: Wiring Loom Layout
Post by: AdrianJ on 01.07. 2019 18:43
Just  finished the wiring, still need to tie everything down.
I was puzzled by the loom and its wiring diagram (not the BSA one from the manual) as it has three wires to the horn! Two brown and one black. Some odd reasoning led me to connect the two brown ones and now the pilot light comes on every time I sound the horn!😀 I'm wondering if this is deliberate.
Also having difficulty securing the main light switch. The small wire clip doesn't seem to work very well.
Adrian
Title: Re: Wiring Loom Layout
Post by: Greybeard on 01.07. 2019 19:07
Just  finished the wiring, still need to tie everything down.
I was puzzled by the loom and its wiring diagram (not the BSA one from the manual) as it has three wires to the horn! Two brown and one black. Some odd reasoning led me to connect the two brown ones and now the pilot light comes on every time I sound the horn!😀 I'm wondering if this is deliberate.
Also having difficulty securing the main light switch. The small wire clip doesn't seem to work very well.
Adrian
On my loom the horn on the drive side has double wires on one terminal. The loom has an alternative horn connection under the tank, so I think that explains the doubled up connection. Why your pilot light should come on when you operate the horn is a mystery.