Loom: buy or diy?

[DanielH]

Hi there,

one of my future tasks on my GT6 mk2-project, is the new eletrical wiring. I have no access to an old harness.

I find the prices for new looms quite hefty (e.g. 360GBP), so I am thinking about a diy-solution. I am not new to auto electrics, but I've never done a full harness by my self.

Additionally, I am planning for a couple of customizations, which would require modifications to the standard harness, e.g.

* 123distributor

* Voltmeter

* Oilpressure gauge

* Electrical fan

* Front fog lamps

* Outlet for mobiles

* E-Type style starter button

* LED lamps and blinkers where possible (smaller cable-diameter possible!)

What is your thinking? Is there a potential to safe money?

thank you 🙂

Dan

 

[NonMember]

I don't think that price is particularly "hefty", when you consider the amount of effort required to make your own, plus the cost of all the cables and terminals. I bought a new loom, with specified modifications, for my Spitfire. If you're making your own, you also need to invest in a whole load of tools, like the correct crimp tools and a loom assembly jig.

[Adrian Cooper]

Hi Dan,

Rob's solution would certainly give you the neatest result. If you have time and want to do something more cheaply then have a look at this 'universal' wiring loom from Car Builder Solutions https://www.carbuilder.com/uk/14-circuit-wiring-loom

They have other types too, some with many more circuit options and relays. A good crimp tool is expensive but the connectors are not too bad. I do agree with Rob that you shouldn't underestimate the time that neat wiring takes to do yourself.

What stage of the rebuild are you at? Is everything apart and access to the back of the dashboard easier?

When I rebuilt my Spitfire I modified a standard wiring loom to include multiple relays and other circuits to a design that I was given by the great John Bonnet (of Lightweight GT fame) How I wish that I had just bought the correct colour coded wires and started from scratch as it would have been much quicker, easier and neater, probably.

Adrian

[DanielH]

Hi there,

what material is required to do a loom?

* 100m cable?

** (2 mm^2 = 0,7 GBP, 3 mm^2 = 1 GBP)

* fuse box (included in harness??)

* 60 bullet connectors (+terminals)?

* 50 addtl. terminals

* Grommets (not included in harness!)

What do you think?

[Josef]

The cable costs go up quite quickly if you want to match the factory colours. I rebuilt my Mk3 loom originally, but spent way more than I anticipated on wire. And it was a big job sourcing all the wire as nowhere I looked stocked all the colour combinations and sizes I ended up needing. If you do want to build your own I’d go for the single colour wire with tagged ends style. Then at least you can buy a couple of reels of various gauge wire and build what you need. Not to everyone’s liking I know

[DanielH]

34 minutes ago, Josef said:

The cable costs go up quite quickly if you want to match the factory colours. I rebuilt my Mk3 loom originally, but spent way more than I anticipated on wire. And it was a big job sourcing all the wire as nowhere I looked stocked all the colour combinations and sizes I ended up needing. If you do want to build your own I’d go for the single colour wire with tagged ends style. Then at least you can buy a couple of reels of various gauge wire and build what you need. Not to everyone’s liking I know

Hi Jo,

  

you'd need 26 colors:

B

B/LG

BO

G

GB

GN

GP

GR

GU

GW

LG/G

LG/K

N

NY

P

PW

R

R/LG

RG

U

U/LG

U/LG

UR

UW

W

WN

WR

WY

😞

 

[Neil Clark]

Yesterday I spent an hour at Spitbitz near Woking - they have a shelf of old Spit / Herald / Vitesse looms from the various years.  There must be commonalities and many of them looked serviceable.  Might be worth a call.  When I built an MX5 powered kit car I bought an old MX5 loom from a  scrappy then laid it out on the drive and tested each section (lights / ignition / etc) and cut out the bits I didn't need (electric windows / additional lights etc).  It gave me the lengths / colours I needed for the replacement segments it needed and costs a fraction of a new loom in both money and frustration!

Might be worth a call www.spitbitz.co.uk

 

[Andyone]

Build your own from fresh using the correct wire colours which will help a lot down the line if you need to trace faults. The OEM looms were made to a price and wire materials have moved on 50 years plus the copper within the wires will be black with oxidation which will run deep if you strip the insulation back increasing resistance. Basically most old looms are on borrowed time and need replacing. 

I'm in the process of doing the same for my TR6 as the cost of a basic loom with mods and relays was ridiculous. Use a good ratchet crimper, dab of solder the joints and heat shrink the join, slide on the rubber terminal boot and then adhesive heat shrink that. Takes time but the results are better than factory plus you can put in as many extra fuses and relays as you wish with some redundancy. All the relays/mods can be hidden under the dash to keep the OEM look if you wish.

In the end I think cost wise my loom will be around the cost of buying a basic loom without mods but will be upgraded and of a better standard plus I will have the satisfaction of knowing where everything is!

Andy

[Colin Lindsay]

32 minutes ago, Andyone said:

 Basically most old looms are on borrowed time and need replacing. 

I'd agree; I have numerous old looms in storage and if you strip off the outer coating a lot is pristine, almost new, but other areas are brittle and worn. I take sections or single cables as needed but I wouldn't put a complete one into a car and expect everything to work.

[Badwolf]

And...remember to fit any rubber boots or insulation, heat shrink etc BEFORE you make up the crimp/joint (and have it the correct way around). Most of us have got to the oh sh*t point when you've made up a beautiful joint and see the boot etc lying on the bench beside the wire, not on it!!

[daverclasper]

Also male bullets etc connections, downstream of insulated females, so if they come undone, won't short out on anything.

I understand this is good practice

[dougbgt6]

It's been touched on already, but do you really want to go with the original dodgy 3 fuse fuse box? A few threads on here regarding replacing the 3 fuse box with a modern 10 blade box. This of course means messing with the loom and it occurs to me that making your own would allow you to put the new box where you like rather than the original bulkhead position. The old one could be left where it is to look original?

Doug