spot light

[tonka]

i am currently trying to fit some front spots to my a bar. i need the power cable to run form the battery to the lights. is it best to fuse the wire through the fuse box. if so how do i go about this. eg how do i get the power into the fuse? can i just run a loop from the fuse next to it or is the job more difficult than this? i am planning on using the "spare" fuse hole in the fuse box. any advice would be much appreciated. thanks

[FridgeFreezer]

1) ALWAYS use a fuse

2) Splicing into the feed to another fuse is not a good idea unless you're certain that the wire is up to the job, is a direct battery feed / ignition switched depending on what you want, and of course you won't be using Scotchloks to splice in, will you? Far better to run a new wire from the battery post / distribution point.

3) ALWAYS ALWAYS use a fuse

4) If you don't want to run wires all over the place, mount a relay-and-fuse near the battery with a short run of heavy wire to the lights, and then you can use a low-current switch and wire to turn the relay on - it's fine to nick that from the fused side of another circuit. You can get inline fuses and relay holders (and relays with inbuilt fuses), waterproofing (if required) is easy enough with a cheapo Asda tupperware box or similar.

5) ALWAYS ALWAYS ALWAYS use a fuse!

[tonka]

so i should run a wire form the distribution point, to the spare fuse in the fuse box, then to the lights using a relay off the main beam?

[Lars L]

Just a friendly advice...

Take the main power from the thick cable connection on the starter. It's closer to the light and cleaner than the battery post which can build up corrosion from the battery fumes.

Then put in a separate fuse holder somewhere under the bonnet where it's easy to get to.

Wire the relay like this:

30 to the starter post

87 to the spots

85 to ground

86 to a live feed for main beam

If you want a switch, connect that either in the min beam feed or in the ground connection. I myself prefer to switch the ground, but that's me... B)

[tonka]

sweet. i'll give that a go

[SteveG]

I myself prefer to switch the ground, but that's me... B)

I can see no logical reason to advise someone to switch the ground connection in a DC circuit on a vehicle with a ground chassis circuit!

Cheers

Steve

[FridgeFreezer]

I agree - unless you're using a transistor, switch to ground just makes more wiring.

[Lars L]

No, you probably don't

But if the 85 on a four post relay where 86 is used as trigger isn't grounded, there isn't much happening in regard of closing the circuit between posts 30 and 87.

Perhaps on a relay made by Lucas...

Switching either 85 or 86 has the same effect. But routing the ground cable through some hole in the body is safer if the insulation goes. But - do as you like, gents.

[LandyManLuke]

I prefer to add all my own wiring direct from the battery, rather than hacking in to LR wiring.

A circuit like this is suitable if you want the lights to be tied into your main beam, with an override switch.

[Lars L]

Well, a good graphic to illustrate what I tried to explain in words.

The difference is in posts 85 and 86, but that doesn't matter. The end result is the same.

[Mark90]

Although it doesn't matter, unless there is a diode, is there a proper recognised convention for which way round you wire 85 and 86?

I normally only switch on the ground if I want multiple switches for the same item, it's often easier than putting in multiple switched live feeds.

[Lars L]

The proper way is live feed to 86 and ground to 85. But as these are the connections to an electromagnetic spool that closes the relay contacts, the other way around is the same thing.

Remember that I'm talking about a four post relay here, marked 85, 86, 87 and 30.

[tonka]

Take the main power from the thick cable connection on the starter. It's closer to the light and cleaner than the battery post which can build up corrosion from the battery fumes.

i dont mean to sound like an idiot but isnt there only power to the starter motor when you are starting the engine

[Mark90]

The big fat cable on the starter is live all the time, it's the little wire that is live only when starting.

[tonka]

yeah spotted it. the biggie is well hidden. all sorted now 2 spots fitted and working. had a little worry with an earth not earthing properley which was well frustrating but its comming along nicly. hopefully it will be ready for the 7 sisters.

[LandyManLuke]

had a little worry with an earth not earthing properley which was well frustrating

You didn't take them back to the battery then? It really is worth doing so.

[TheBeastie]

Hi - not intended to be a hijack but trying to clarify a wiring principle mentioned extensively in the thread about running cables directly back to the battery.

Presumably the way you do this is put say a 6 way fuse holder in the battery box for the live connections and run three thick (e.g. 4 sq mm) brown cables and double up two connectors to each wire so that you have one side of the fuse box live, pop 15 amp fuses in, and then run long 4 sq mm cables from the fuse box to the front where they get used to feed power supply to the relays - but run the cables through one of the convoluted plastic tubes for protection.

As for earth then same sort of approach (and cable size) but somehow aggregating the cables before connecting to the battery so that there are not loads of ring connectors bulking up the battery clamp.

Is this the right sort of approach?

If so, then I need to re-think my wiring which is not an issue but would rather get it right second time round!

If it is not the right way then can you put me right?

Thanks and sorry if it is too tedious for words but sparky wires do not do a lot for me!!

[LandyManLuke]

Bus bars are a nice way of doing it, even if they're not cheap. i like them.

You can see my -ve bus bar in this picture

[TheBeastie]

Hi Luke

So is that effectively a distribution box you have on your bulkhead behind the seats in that big black box? With multiple power supplies coming directly off a +ve bus bar inside the box and feeding out to that fuse box - with presumably outgoing live, but fused, feeds on the other side out of sight.

The -ve bus bar looks like something that could be quite easily fabricated or is there more to it than meets the eye? Clearly for a +ve you would need to have some rather sound insulation I would think!!!

Is there any reason why you have done this out of the battery box i.e. is it safer, no space in box, easier to get at etc?

Also, just to be pedantic, was my perception of how to run the wires right?

This electric stuff is beginning to make sense but still more to it than I keep thinking!

Thanks for the picture which did help.

[LandyManLuke]

For the purposes of this thread, ignore the black box, its a PC-Relay interface. Hence the parallel cable on the left hand side.

Yes you could make a bus bar, or Durite et al stock different versions, stud, screw,4,6,8,10,12 etc. you can get bus bars intended for +ve use, they come with a shield that fixes over the connections. The negative bus bar i have is insulated from the bulkhead, its base plate is plastic.

It's where it is because the battery box has two batteries in it, and the bulkhead is higher and thus (most of the time) drier.