9 replies to this topic

[Metrodave2020]

I have followed relevant posts on TMF for wiring front spots and fogs and a few other items, however translating this to a shopping list is the tricky thing for me, particularly wiring.  It would really help before I order if someone could comment that I’m heading in the right direction.  I am wiring 3 Lucas 576 lamps each with a 48w LBL323 bulb (so approx.. 4amps each) and the other items – are the wire gauges (quoted in AWG) I have suggested appropriate?

1. 1 x spot through the main beam 4 amps 16 gauge
2. 2x fogs through dipped beam 8  amps     14 gauge
3. 1 x reversing light through the remote gear switch 4 amps            16 gauge
4. Voltmeter            16 gauge
5. Cigar Lighter 12 amps (although as only for satnav etc will draw much less)            14 gauge
6. Radio 3 amps     14 gauge to harness
7. Panel lighting to additional gauges and illumination circuit for car radio   2 amps 18 gauge

My shopping list is

1. 1 x 4-fuse blade-type fuse box
2. 3 x 20 amp fuses (for fuse box)
3. 3 x 12 amp fuses (for inline fuses to the light)
4. 3 x 12V Relays – 30 or 40amp?
5. Cable as above
6. Heat shrink sheathing

I already have a crimper and selection of connectors

 

My queries are:

1. Does the above list cover everything?
2. Are my suggested gauge sizes correct?
3. Should the supply from the solenoid to the fuse box be a smaller gauge, say 12?
4. Is there a way of only attaching one cable from the solenoid to the fuse box, just to reduce the number of connections leading to the solenoid?  If so, what size cable and presumably this can be fed to a junction box by the fuse box?
5. Can I use the same cable size for earth throughout e.g.   14 or 16 gauge?
6. Do the single Lucas 576 lights for the spot light and reversing light need to go through a relay?
7. When cabling is sold and not described by AWG sizes, am I looking for ‘thin wall cable’?  Some of the descriptions I’m afraid totally confuse me and different suppliers appear to have significantly conflicting details for something purporting to do the same job.  For example, https://www.autoelec...70/category/114 states has12/0.20, 0.35mm², 7.0A - cable OD 1.4mm…for starters, what do 12, 0.20 and OD mean?   This seems inconsistent with  https://www.holden.c...er_metre_8/0.30, that says it is suitable for 8 amps but the area is quoted as 1.0mm².   So which would be right for the 8am supply to the 2 fog lights?
8. What size heat shrink cabling am I looking for?

I would appreciate any help!  Many thanks in advance.  If you would prefer a PM, then that’s fine by me.  If you have had good experience with a particular supplier or any of the above product that would be great.

 

I hope everyone is having a Good Easter weekend.

 

Cheers

 

David

 

 

 

[lordcakes]

Hi David, many question but I will try to answer as much as possible.

Cable sizes, may be expressed as total cross sectional area such as 1.0mm, 2.0mm or as an AWG size or in a format such as 12/0.20; the latter is similar to the first except that is shows the number of strands in the cable and the csa of each strand.

In terms of sizing your cable, you can go bigger than your maximum current draw but never go smaller. Fuses should be a lower rating that your cable rating. Manufacturers will go for different sized cables depending on the circuit capacity as a cost/weight consideration. If you are doing a small amount of wiring you may just want to pick a size (eg. 2.0mm) and use that throughout.

What I don't see on your list is how you are going to feed your fuse box. If you are going to add these circuits off existing wires/circuits then you could be overloading them. You would be better to use a fuse box with a busbar system and feed that from the battery or solenoid.

Your light circuits should be fed from a permanent live circuit and switched via a relay (switching feed comes via the original lighting circuit)

Your voltmeter can be fed directly from the instrument feed (white wire) with a 3a in line fuse.

Your radio will probably need a permanent live feed as well as an ignition feed.

Your cigar lighter should probably only work when the ignition is on (unless you want it to be permanently live).

You will likely have a white/green wire at your ignition switch which can be used to trigger a relay for the circuits not wanting to be permanently live.

I would suggest 2 x 4 way fuse boxes for what you want, each with a bus-bar feed (feed from the battery would be 4mm or 6mm cable based on total rating of your fuse box). The first would be used for driving lights, fog lights and radio permanent live. The second would be used for reversing light, radio switched live and cigar lighter.

My suppliers of choice have been Auto Electric Supplies and 12volt Planet, depending on the exact products that I have wanted or availability.

Use good quality crimps, preferably uninsulated ones and use the separate boots over the connector. For relays, they need to be higher rated than the circuit so I would use 30a for the lighting feeds but a 40a for the ignition switched fuse box.

This might raise a few more questions for you, especially in design of circuits and fuse boxes (and where to locate them) but I hope it helps.

[lordcakes]

Something like this would also work well depending on space or layout

https://www.autoelec...701/category/63

[Metrodave2020]

Hi lordcakes, thank you I now understand the description of the wiring and will purchase on the basis of the appropriate csa.

 

Thank you too for going through the lengthy questions, I perhaps should have added in the initial query that it's a 1986 Mini and has the 4 fuse box.  I hadn't heard of a busbar but that seems to address the issue of having multiple cables from the solenoid.  I have space, I believe, for the additional 4 fuse box and three relays to supply the front spot, two front fogs and the reversing light.

 

Thanks for suggesting the how to wire in the voltmeter and radio.

 

The other queries I'll ask the supplier, again thank you for suggesting a couple.  I have to say I rang one big supplier and maybe it's just the person I spoke to but they could not explain the description of the wiring available on their own website.

 

Just one final query, is it a big downside to use insulated crimp connectors with integral boots?

 

Cheers

 

David

[lordcakes]

David,

Uninsulated crimps give you the best mechanical (and therefore reliable) connection. However, the insulated one aren't bad either, just not quite as good. That said, I've still got quite a few of these in my car and they have proven to be pretty reliable.

If you are going to use the insulated ones, use a decent ratchet crimp tool, not the plier type ones.

[gazza82]

My preference would be uninsulated with heat-shrink tubing.

One spot? Do they not need to be fitted in pairs?

[PoolGuy]

One spot? Do they not need to be fitted in pairs?

No, you can fit a single as long as it's central.

[Metrodave2020]

Thanks, yes the spot will be central which I understand is OK with applicable regs.

 

There's a multitude of shrink wrap tubing...what size should I be looking for?  Cheers

[lordcakes]

Shrink-wrap tuning will generally be shown in 3 ways depending on the seller:
1. A simple size which is the unshrunk diameter of the sleeving
2. Two sizes, shrunk and unshrunk diameters
3. A ratio showing how far the tubing will shrink (and usually the unshrunk size).

I can't really advise a specific size as I don't know exactly how you are going to use it and what cables you have but as a general rule go for the smallest size that will fit over what you want to seal. Buying a multipack is often the easiest way to go, available on amazon, ebay and places like toolstation.

[PoolGuy]

If your shrink wrapped joints will be exposed to the elements I’d use the adhesive lined variety, it’s got a higher shrink ratio which means that you’ll need less sizes too. For what it costs I’d buy a meter of 3-4 sizes, it’s always useful stuff to have about. https://www.polevolt...k_Sleeving.html