Please visit the Club's website https://www.dloc.org.uk/ to join. Visit https://www.dloc.org.uk/adhoc to DONATE towards the cost of the forum.
Please don't post someone's email address to avoid it being harvested by spambots and it's against GDPR regulations.
Always look at "ACTIVE TOPICS" to see all posts in date & time order as they are sometimes moved; or look at "Your Posts".
Please add Reg. nrs. when posting a photo or anything about a car as this will help searches. Don't add punctuation next to nr. as this negates search.
CHANGED YOUR EMAIL ADDRESS since registering?, click your username and check your address in User Control Panel, Profile, Account Settings.
If you want help to register, use "contact us" at page bottom for help.

wiring rating

Technical issues not related to a DLOC car marque, eg tyres, ethanol, other car makes, etc. and legal, political and insurance
Post Reply
Db n j
Wise Man
Wise Man
Posts: 919
Joined: Sun Mar 13, 2016 8:55 am
Location: uk shropshire

wiring rating

Post by Db n j »

I want to rewire the horn/indicator assembly for a Special Sports. I looked at the braided cable from Autosparks and others, but was unsure which thickness or
rating I need ( Horn, Indicator Live / Left/Right, Earth)

Can anyone recommend a quick reference table (thickness/rating - application, and recommendation for a supplier in the UK please.

Thanks

db

Simon Hyslop

Re: wiring rating

Post by Simon Hyslop »

A WT614 horn works at about 5.5 amps, so two of them are 11 amps. 28/0.30 cable is rated at 17 amps, 14.030 cable at 8.75 amps. I can't say I've ever felt that original or replacement stator tube multicore cable contained wire of 17 amp capacity (but I could be wrong) , the usual line of thought with the horns being that they are only used intermittently so there is little chance of the wiring going on fire because the passing current lasts only a brief time. As the horns are permanently live, the cable in question in the stator tube wiring is an earth wire so presumably it has been thought of as a rather lower risk.

Indicators ? 21 w x2 + say 5w for a warning lamp = 47w = 4 amps so 9/0.30 cable would be adequate rated at 5.75 amps, half of that for each side. If there are trafficators too, they use 2-3 amps each, so 14/0.30 would cover the supply in all eventualities.

I have noted that Autosparks have never listed the capacity of their stator tube wiring so it might be worth asking them what the actual capacities are.

Three possibilities are (not exhaustive) : fit a relay to switch the horn earth, thus removing the need to have any heavier draw on the whole circuit going up the steering column.

Fit a five core cable using 9/0.30 wires, bearing in mind the limitation if using trafficators and indicators. Fit two of them to the horn contact and that will give you a capacity of 11.5 amps which should be enough for two windtones. I am making the assumption that it will fit the tube but on the basis that 4 core fits with plenty of room to spare, I would have hopes that the five core cable would be all right.

Make up a harness using wires of the correct rating and just bind them neatly with cotton harness tape, neatly because space in the tube could become an issue but if you use thinwall cable, you should be able to increase the load capacity without unduly increasing the bulk.

If you want one supplier for all the wires in all the right colours, I reckon buying from Autosparks is probably the best choice. However, if you want a fair selection of colours in larger quantities at more reasonable prices, I use Beal :


https://www.beal.org.uk/automotive/auto ... x-30m.html

as you can cover quite a lot of the automotive standard colours from their range and their thin wall cables are very useful if you are adding extra cabling for indicators etc. to go through existing holes and grommets.

In case someone reading this is thinking of making one of these harnesses, I'd just mention that the bullet end of the harness should have the bullets in a staggered order, to make them fit down the tube easily. You can fit them afterwards if you've only got access to the blue or red crimp type but the right way is to use brass bullets with a proper bullet crimper or to solder them on. More of a difficulty, and not be dismissed as a two minute job, is how to make the ring fittings at the steering wheel end. The plastic crimp types are, I think, quite unsuitable for this because the cable needs to bend at right angles in a very small space. Neatly soldering the wire to itself in the correct diameter ring would be preferable, unless you have access to very small ring terminals which can have the wire soldered securely and then put a piece of heatshrink round it just in case. Originally the brass nuts securing the four terminals were soldered over and this is a good idea. The reason is that the whole assembly is subjected to quite a bit of vibration and if the live trafficator wire comes loose or the horn earth comes loose, either will give the driver quite a shock, aurally or electrically!

Db n j
Wise Man
Wise Man
Posts: 919
Joined: Sun Mar 13, 2016 8:55 am
Location: uk shropshire

Re: wiring rating

Post by Db n j »

Simon, many thanks, that’s really comprehensive. I will study again, and make some notes. I am no electrician, so appreciate the input.

Post Reply