Amperage of Wiring

[Howard]

I want to rewire my `51 A7. I have a wiring diagram however I`m not sure which amperage wire to use. Halfords sell 5, 8, and 17 amp wire. The old loom has been hacked about, most of it looks 17 amp type but not all of it, could I use 17 amp wire right through ?

[iansoady]

The heavier the wire the less the voltage loss in it. I tend to err on the heavy side, and it certainly won't do any harm.

Try Vehicle Wiring Products who have a thinwall cable which is useful if space is tight.

[BSA_54A10]

your bike is fitted with a 60W or 80W dynamo.
Divide the watts by 6 Volts and you get 10 to 15 Amps.
This is what is required for the wire from the regulator to earth and the regulator to the amp meter.
Your headlamp should be 35/25 W, again divide by 6 and you get 6A or 5.2A.
Tail lamp 5/25W and on it goes.
If you have done a 12V conversion the you are looking at 1/2 the amp rating.
I usually use 10 A wire for every thing but we rate wire differently down here.
Heavy wire ( to & from ampmeter  ) 28 strand.
light wire ( every thing else ) 14 strand wire.
If you are going to do it yourself seriously consider fitting 3 fuses at least
1 on each of the feed wires to the amp meter and another on the earth.
Also consider using modern blade terminals in blocks which makes undoing joint much easier.
I also wire the battery to a plug and paint the battery terminals with "Liquid electrical tape" thus you get no corrosion at the battery terminals.

[Dynamo Regulators Mike]

My take would be to use the heavier wire for lower losses:

• From the dynamo D to the regulator, then from regulator A to Ammeter. (If you use a small electronic regulator it can be fitted between the upper frame tubes under the tank to reduce the path resistance further and free up space in the toolbox.)
  
• Then to lights switch and dip-switch to headlight. (Even better use a relay {or 2} to switch the headlight supply.)
• Definitely take a good earth wire back to the dynamo to complete the circuit.

Fuses are a very good idea for protection of all the good work.

[RichardL]

Trevor,

For the electrically impaired, strand count is not a particularly good measure of ampacity, as I am sure you know. You can get #24 AWG microphone cable with a strand count of 105 x #44 AWG, and that would be good for about 2 A, max, in a taped or tubed loom.

For 15A, #14 AWG or #16 SWG should be fine. Go 12 or 15, respectfully if you want even more margin. For 6A, you could go as small as #20 AWG or #21 SWG, but I would move up to #18 AWG or #18 (or 19) SWG, just to have more physically robust wire. Incidentily, again for the electrically impaired, use only stranded wire. The actual strand count is not so important, but keep it higher than house wiring (for good flexibility). After all, we are not concerned with high-frequency skin effects. If there is no one here whose doesn't already know these things, I am sure there is a mythical ficticious A7/A10 owner who is thanking me right now.

Richard L.

[Howard]

Thanks all for the input...regards Howard

[900triple]

• From the dynamo D to the regulator, then from regulator A to Ammeter. (If you use a small electronic regulator it can be fitted between the upper frame tubes under the tank to reduce the path resistance further and free up space in the toolbox.)
  

Would said small electronic regulator be safe in the headlamp shell? Or does it need to go in the airflow??

I'm just about at this stage with my A7 rebuild and the timing of this thread is perfect!

[RichardL]

As far as I can tell, the DVR2 does not need to be in the airflow. The headlamp shell is not sealed. Here is a link to a couple of installs, including mine, which is in the original regulator case. It is mounted in the original regulator location.

http://www.a7a10.net/forum/index.php/topic,472.msg3927.html#msg3927

Richard L.

[Dynamo Regulators Mike]

In the case of the DVR2 it barely gets warm at a full 8 Amps output. It would be fine mounted in the headlamp shell. As Richard says it is not sealed so may offer better cooling if anything than the toolbox position.
The aluminium case of the current unit is 56 x 33 x 18 mm so it should fit.
Of course I cannot vouch for other units, some of which run very much hotter, and heat is the death of electronic components.

[RoadRunner]

Try Vehicle Wiring Products who have a thinwall cable which is useful if space is tight.

Autosparks are better in my experience; cheaper and will sell most components in small quantities unlike VWP who sell in 10's! Blade fuse holders from Autosparks were not far off half the price of that of VWP.
They stock all different sizes of bullets, wire colour and thickness - tools are also cheaper!
10 mins from J25 M1 in Sandiacre. Small bits made while you wait - fantastic service!

http://www.autosparks.co.uk/

RoadRunner

[iansoady]

Autosparks look good - many thanks.

[BSA_54A10]

And if you are a stickler for originality ( I am not ) you can also still get the tin coated wire originally used at most good boating suppliers.
An ex member who liked "messing around in boats" drew this to my attention.