I'm in the process of rebuilding my 88" series 3 and need to re-wire the whole vehicle. Can't really afford a whole new loom from the likes of Autosparks and want to do the job myself encorporating an EDIS system and mega jolt. I realise that this is a big job but still want to give it a go as once completed I'll be able to modify or repair relatively easily. Should also mean that i can make the electrics relatively waterproof to take advantage of the EDIS. The engine is a 2.25 petrol. I know that whilst I'm planning the wiring system I need to calculate what cable to use. I know that i can culculate the ampage of wire required but need to know the watts consumed by the equipment to be supplied. How can i work this out so that I can work out what wire to use? Any help would be really appreciated.

The wire should be rated by the supply fuse rather than actual power consumption.

What Jimmy said. You want the fuse to blow before the wire gets hot.

I was going to write out a list of wattages but realised it's be easier to write out a list of which wire to buy you can find all the correct colours in the Series green bible or haynes manual, I'd suggest sticking to them to make your life easier in future. You may well find a loom from Autosparks works out cheaper than buying it all individually and doing it yourself.

Headlights main beam - 2mmsq
Headlights dip - 2mmsq
Starter solenoid - 2mmsq
Everything else - 1mmsq (you can get away with .5mm for some but it doesn't come with a tracer colour which makes life trickier later)
This of course assumes you're using thinwall cable as sold by VWP.

as previous posts, but id definately make sure you buy a range of colours, dont stick to red and black-youll regret it when the first fault comes along

The relationship is :

W = VA

Where W is in watts
V is in Volts
A is in amps.

Unless a cable is only used for a very short time (eg windscreen washers) it should have a capacity of at least twice its expected load - to prevent it running hot. Thought should also be given to the effect of heat build up in looms especially after prolonged use - ie several hours running.

Whilst I appreciate that the primary purpose of a fuse is to protect the device running off it (well that's what car manufacturers will tell you but I think they lost the plot many years ago) I would place the fuses as close to the battery as reasonably practicable. The reason is that vehicles do develop wiring faults and if there's 10 ft of wiring and multiple junctions and looms before the fuse there are may opportunities for damage - and also damage to looms etc should one wire overheat.

Had a Triumph Stag (with many fuses) catch fire due to a fault under the dashboard - removed all fuses - still feeding current. Renault 21 fan seized - fused 75 amps (correctly as it was on a circuit with just about everything else) and it burnt out a limb of the loom running from the dash to the4 radiator and damaged the main loom. (Fun afternoon in front of the TV taking it apart and soldering in new wires!)

Bloody hard one this question re wiring would be a nightmare but possible cable sizes would vary for each different circuit the watts calculation is easy but finding the cunsumption of each item would be more complicated i would imagin. not exactly sure of the situation but re wiring bit by bit would be recomended so you would know the cable size unless your an expert .you could use electrical cable 6491x which is a little cheeper then auto cable but not as well rated and slightly mord difficult to use work out the benifets and select to suit .i agree coulering is important but you could use marking sleves or 3m tape markers if you liked

Err, it's not that hard - you've only got a few cable sizes to choose from (.5, 1, 2mmsq) and the lack of tracer on .5 rules it out for a decent job. Proper thinwall cable is about 23p/m last time I looked which isn't going to break the bank. Then again, Autosparks looms aren't exactly pricey for what they are.

You should NOT use 6491x cable as the smaller sizes are usually a single solid conductor, this is not good for a vehicle as it's subject to vibrations which can cause the copper to break if it's one solid bit.

no 6491x is single core its all got 7 strands and it was only a money saving sugestion as was using the old loom to gauge cable sizes makes sence really

Apologies - the spec I found was written as if it had a single solid copper conductor. However, it's still not quite right for the job, it's still quite rigid stuff (7 strands compared to 30+ for thinwall), the current rating is lower than thinwall and the spec says it's designed to go inside protective conduit and work up to ~70C, which is a bit different to being under the bonnet of a LR.

Thanks for all the advice. It's great to find so many well informed people who are willing to take the time to share their experience.

If I learn only one thing today - let this be it!

So simple !

Thanks FF

Hi,

I rewired my Lightweight using the remains of one two Range Rover harness! They came with a nice blade fuse box also.
There was enough fuseholders for all normal stuff along with acc such as fan/spots etc.

If rewiring i would suggest a set of relays. For headlights dip/full, electric fan, horn to name a few!
Buy some holders that can interlink and will make it nice and tidy. You can get the connectors to go with them to customise your install.

The only problem with the RR fusebox is no available connectors are readily available.. that i know of. unlike that from Vehicle wiring products that use standard lucar crimps. I was able to remove the connectors from the fuse holder though and used a combination from a few harnesses. (Try get fuse/fusebox as close to battery as possible).

The beauty with the RR harnes is that it had correct colour codes and weight/amperage that i was looking for.

Get yourself a nice mulitmeter and a quality crimp tool. Worth the investment if you going down this road!

You will need to check any used wiring before putting in cct though. Steer clear of wires that are black copper or stiff.

Oh i also used recycled sleeving to fit cables in. DONT wrap cables in insulating tape! Good idea i know, nice and tidy today but nasty and sticky next week.

If you need some more help give me a shout.

Just a couple of points - VWP make a number of relay bases which use what looks like a Lucar connector. In fact it has a locating tag - which means you can fit the terminal, then push the relay into the holder and the terminals stay put. Use a standard lucar - and they'll fall out. The terminals are supplied with the bases.

The correct crimping tool is well worthwhile. If you solder the terminals they may not fit the holders unless you're very careful (get lumps on etc.)