IM CURRENTLY AT MY WITTS END!
I'm coming to the end of building my truck from the ground up and am faced with the wiring side of things, the truck was originally a 2.5na but has now got a 300tdi fitted so my question is what's the best loom to put into my truck as my current one has been fully stripped out due to setting on fire!

A. Is it best to stick with another 2.5na wiring loom and modify to fit the engine

B. Fit a 300 tdi loom and modify/ change all instruments

C. Find someone to do the wiring for me as I've had enough


I've invested alot of time and money into doing everything the right way whilst doing this build so just want the best advice to move forward with.

Thankyou in advance

Nobody can really answer this fully. Really depends what has been done to your vehicle. And what your are wanting to wire in.

Also there isn’t a single loom. There are many parts to it. A later style blade fuse box might be a sensible upgrade. If you don’t really know/not confident, get an auto electrician to do it.

Thanks for your reply, I'm literally wanting the most basic of looms with the basic warning lights etc

The truck is fitted with uprated head lights and front and rear light bar.

Was originally a 2.5 with a lt77

So currently everything inside the cab is the rubber bullet push connectors (not certain on there name)

Now a 300tdi mounted to a defender r380

I will be running a split charge kit also

I'm a dab hand with the spanners and not overly complicated wiring (extending looms etc)

I've approached loads of auto electricians around my way and offered them the job and they all want new stuff they can jusy plug in

Headlights can benefit from running via a relay. There is a wiring kit for this. But not overly difficult to make.

Likewise with the light bars.

There should be an engine loom. Although it is only a few wires. One to suit the engine would make sense. But haven’t you got this already? Alternator wiring may be part of this. But depends what you have done with the alternator.

Dual/split charging will all be custom. And dependant on your setup. Is this an overlander build?

Then you have the loom down the chassis. Normally would be feed inside the chassis leg. But is a lot easier to run along the top of the chassis.

You have the front loom for the rest of the engine bay that isn’t the engine.

And the loom behind the dash plus fuse box.

Do you need to replace it all or is some/most of it perfectly fine?

Id go 300 loom, and get blade fuses etc.

If you change the headlights to LED (either a drop in bulb in standard housings or all-in-ones) you dont get the heat at the connector.

I can see no bonus to keeping the older loom if your going to be changing the temp sender etc as it is - the thread on the 300 is different, so you cant use your old sender, even if you had it... which then means you need to change the gauge anyway - i mean thats not a loom issue anyway, as a spade connector is a spade connector, but i just see no reason to keep the old loom design and have to change bits of it - may as well just go 300.

ps bare in mind that a 300 loom from autosparks is insane money, so look up the costings before you get too carried away

Just swap the engine loom over from the old engine.
Plug it in and no major expense needed.

The engine should make no difference really.
You need one wire for the starter motor solenoid trigger from the ignition switch.
You need one wire from the dash to the alternator for the warning light.
One heavy cable from the back of the alternator around the back of the engine to the starter motor positive terminal.
And one wire for the temperature sender.

deccyb said:

B. Fit a 300 tdi loom and modify/ change all instruments

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I have just done this with mine after an engine fire (link). I fitted full 300tdi looms throughout despite running a 200tdi engine and being a 1989 TD vehicle. You do not need to change all of the instruments, there are several variants available on the autosparks website, the latest model 300tdi ones have the td5 style white multi spade connectors rather than the rubber bullets (this is what i fitted) however the only difference for this in terms of instruments is that you need the later style column switches (wipers, indicator, headlight). Because I have an older vehicle I also needed to fit the later style vehicle lights (I went for LED at the same time) as the connectors change from the bullets to the econoseal plugs. You can do this by fitting newer lights and drilling out the correct holes in the body to fit, you will need to drill a larger centre hole if using standard lights (not needed if using LED) and you will need to drill out square holes to fit RTC3745 to mount them. Alternatively you can use the old style bullet lights you already have and use an adapter loom (LINK)

As above bear in mind the vehicle has three looms:
Engine loom
Rear chassis loom
Main bulkhead wiring loom

The engine loom does the engine wiring (alternator, sensors etc) and is best matched to your engine but you will need to make sure the plug on it to connect to the main bulkhead loom matches relatively easy to modify and/or change the plug if required.

The rear chassis does the rear lights, wiper and heated screen (if fitted) again you will need to make sure the plug on it to connect to the main bulkhead loom matches relatively easy to modify and/or change the plug if required.

Both of the above are comparatively cheap and and easy to modify to match the main loom. The main loom does everything else, has the fuse box on it and is the most expensive to replace. In my opinion your choice of main loom dictates how much work everything else is and the easiest route, all be it the most expensive, is to get all three looms to match.

After the fire you had are all three loom destroyed or do you still have one or more of them fully intact and usable? the answer to this will guide the advice. If your current main loom is fine then then the best option might be different to if you are starting form scratch. Also as mentioned the new looms are not cheap and prices have increased significantly in the two years since I bought mine.

So the loom that's was in the truck has been fiddled with from every man and his dog from the look of it so I'm not overly confident using any what part of this, I understand that I need to source all 3 of the looms and think I could adapt/modify/Buy nee instruments if needed,

I'm going to be running light bars on relays and the head lights are the all in one led powered ones,

So from reading everyone's replies I think the best thing to do is to look for a 300tdi loom main&engine and chassis?

Also if anyone's local to Manchester once I've sourced all three there will be money and beers aswell as dinner if anyone wishes to guide me along the way

Also does anyone know anywhere I can source any of the above?

autosparks. but the bulkhead loom is about £1k

if your bulkhead loom is salvageable, get it all out of the car, and onto the kitchen (etc) table, with a battery connected up, the bulbs etc in place, and a wiring diagram.

go through it all, and work it out, and repair it. if you can do that, youll know it better, and youll save yourself a grand.

or, if you have loadsamoney (or whatever) just go buy an autosparks one


note - i saved my 300 bulkhead loom by "kitchen tabling" it, but ill buy a new chassis loom (way way cheaper) from autosparks when i do the chassis

julianf said:

autosparks. but the bulkhead loom is about £1k

if your bulkhead loom is salvageable, get it all out of the car, and onto the kitchen (etc) table, with a battery connected up, the bulbs etc in place, and a wiring diagram.

go through it all, and work it out, and repair it. if you can do that, youll know it better, and youll save yourself a grand.

or, if you have loadsamoney (or whatever) just go buy an autosparks one


note - i saved my 300 bulkhead loom by "kitchen tabling" it, but ill buy a new chassis loom (way way cheaper) from autosparks when i do the chassis

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Unfortunately I think mine is beyond the kitchen table surgery, it's missing allsorts some stuffs burnt out and i think I'd be asking for trouble putting it back in I have seen the autosparks looms and aint to keen on the price I think it's a bit of a rip take, I'd be looking for a decent second hand loom if I was to purchase one

julianf said:

autosparks. but the bulkhead loom is about £1k

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I will dig out what I ordered for mine but again I got them from Autosoarks. If that is the current price it has doubled since I did mine! I

deccyb said:

Also if anyone's local to Manchester once I've sourced all three there will be money and beers aswell as dinner if anyone wishes to guide me along the way

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My rebuild thread linked above has all of the work detailed with pictures of nearly every connector and what they go to. You can also see on that thread the relay box and fuse box I added for the additional lighting etc I fitted.

Also as a side note if you use a later model wiring loom I think the headlights are already on a relay rather than direct through the switch. Even so led light reduce the current draw on everything which is why I fitted them.

Thanks for the help lads I'm gunna look into the 300tdi loom any more advice is welcome