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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Custom wiring harness

FWIW: I have revised and upgraded the design of the custom wiring harness that I published in the May 2001 issue of the British V8 newsletter. The complete "how-to" instructions for building this wiring system may be found at http://www.britishv8.org/techhome.htm

This is a 14 page document, in pdf format, with complete instructions for building a relacement wiring system for any British car, but the instructions use an MGBGT as the example. A complete list of parts is provided, along with the source and price of the parts. The design includes an easily fabricated, home-built panel, with 6 relays, 8 fuses, two flashers, and a power terminal. Total cost for the parts will run around $300, and includes ALL the wire needed to replace every wire on your car, maintaining the orignal MGB/Lucas color code.

At the risk of being hunted down by the ethics committee and boiled in oil for advertising, I want to let everyone know I will soon be offering for sale complete kits of parts for this system, using a better grade and larger gauge wire than can be bought by individuals in small quanities (I buy wire in 1000 foot spools, and I have purchased over 85,000 feet of wire for this project), and a pre-fabricated mounting plate, but the price will be competetive with what you could buy the parts for yourself. I'll also be offering a few pre-assembled kits as well. Pricing and availability TBA.

I'm not doing this to make money, so I don't care if you buy from me or from the sources listed in the article, but either way, I recommend you take a look at the article and see if this is something for you. I only want to sell enough to recover my investment and to help other British car owners.

One of the things I dislike most about an MGB is the rat's nest of wiring under the hood. This will get rid of that, and give you a modern, reliable, wiring system, with the fuses, relays, etc, mounted inside the car, out of site and out of the weather.

Regards,

Dan
Dan Masters

It sounds great, Dan!

I went to your site and it did not seem to want to download the PDF file. I will try again later.

The only question I have is what sort of wire are you using? THHN? I just wondered as this has worked well for me over the years and seems more resistant to the abuse of the engine compartment and road than other types of auto wiring I am familiar with. If you are using fewer breaks in the wiring between the battery and components as you mentioned in another thread, then it certainly will be an improvement. There are plenty of folks who will welcome an alternative.

Bob Muenchausen

If it really is good and better than what is available - then you really should make your profit from it. It wouldn't bother me at all to get good well thought out parts.
Marc Gander

Excellent job Dan. I quickly went through the document and it appears to be a nice alternative. The cost is equivalent to a new harness. I will look at it more in-depth later. Nice diagrams and photos. I will be rewiring this winter and have not yet set my coarse.

Thanks for sharing.

-mike
Mike Zaffarano

Bob,

That's a problem with pdf files and MSIE - if you click on the link, you get no indication at all that anything is happening - it appears as if the link isn't working. Be patient, and it will download, but it may take several minute. You might want to right click and choose "save target to...." It doesn't download any quicker, but you do get a progress bar to look at while you wait, and to confirm that something is actually happening.

The wire that I am using is type SXL, a cross-linked polyethelene, oil, grease, and gas resistant wire, rated to 125 degrees C (257 F). Standard wire is PVC. The wires have a spiral stripe, rather than the normal longitudal stripe, so it is much easier to read the color codes. Sometimes, with the original wire, it is hard to tell, for example, if you are looking at a white wire with a purple stripe, or a purple wire with a white stripe. Also, if the strip is turned towards the inside of the wiring bundle, it's hard to see. With spirals running on a 1 -1/2 inch base, it's pretty easy to spot the stripe.

The company I buy my wire from is the same company that sells wire to painless and others, but Painless uses a thinner wall insulation than I am using. If you are wiring up a new Mercedes Benz or Cadillac, - or a street rod - with all the fancy electronic functions, thin wall insulation is desirable to keep the bundle size managable, but for our cars, even with added accessories, the thin wall is not justified.

I hope you're right about the interest in it - I originally intended only to wire up a few cars for myself and some friends, and couldn't justify the cost of the wire, but I went ahead anyway, hoping to be able to sell enough later to recoup my costs. 85,000 feet of wire costs a LOT of money! I have a few thou$and invested.
Dan Masters

Dan,
Nicely Done!!! I recently bought a bone stock '74 roadster. Most electrical things still work but just barely.

I was surprised when I figured out that the fuse box + all those in-line fuses were stock. Why they didn't build a bigger fuse box I can't figure. Maybe they got the fuse boxes from the same supplier as the 6 volt batteries. Just adds to the character of the B.

I'll definitely keep you in mind as a plan my attack.

PaulP
PR Peterson

Dan

I will be rewiring my 69 C in the next few months after a complete strip and dip of the body prior to painting. Would like to know when you do have the parts and pieces available for purchase. Do you have a "sign up for later notification" list? If so, pleae add my name to it.

Thanks

Larry

69 C in restoration
Lawrence Hallanger

Dan, Nice work. I do have some questions and a comment.
1. Is there some brand name we should look for when looking for a factory style crimper shown on page 6? Is it similar to the one British Wiring sells?
2. What type terminals is the GB crimping tool on page 7 used for?
3. I noticed a large number of bullets in the parts list, do you suggest the big bundle of bullet connectors presently located near the firewall in the right fenderwell be relocated to some other location?
4. Last Friday I went to a breakers yard and bought a first inertia switch from a Ford Taurus to use in my
68 GT. The Ford switch is a quality unit compared to the ones I have seen in TR 8 which I think is the same as used in the later MGB's. I have been using a Ford switch on my 74 for over two years. I paid $5 for the one I bought Friday. Just a thought for someone wanting to save a little on the suplies. Chrome bumper cars did not have a first inertia switch and in my opinion they are a good safety feature for any car using an electric fuel pump.

I do appreciate you taking time to write about electrical systems for us to read. Your inputs have been helpful and informative for me.

Thanks, Clifton
Clifton Gordon

Larry,

I'll be posting a price list and delivery schedule on my website in a few days. I'll let everyone on this BBS know when it goes up. I have most of the parts and pieces now, so if you want to get only the part/pieces, they would be available as soon as I work out the costs. If you want me to build you one, it'll be a bit before I can see what my schedule will allow, but it should be fairly soon. I have a few in the pipeline now that need to be gotten out soon.

Clifton,

1. I don't have a brand name or source for that crimper, but i see it from time to time on various electrical catalogs. Waytek, for example, carries them. I bought mine many years ago, and stuck it in the back of my toolbox because I didn't realize what it was good for. I had been trying to crimp standar termnals with it, with no success.

2. The GB tool is used for crimping standard uninsulated terminals.

3. The bullets that I list are for the various light fixtures, such as the turn signals, back up lights, etc, as these come with bullet terminals on them. I prefer to splice the wires to these lights, and not use any terminals at all, but it makes it hard to remove the lights if you need to replace them or do body work. The fewer terminals/connectors you have, the better off you are. That bundle of wire, fuses, bullets, etc, that you mention will be gone with this kit. you'll see nothing under the hood but wire, neatly routed and protected by either tape or split loom.

4. Using an inertia switch is a good idea, but the ones I have found available new are rather expensive. No reason at all not to use junkyard items. $5 is better than $50!
Dan Masters

Dan,
Thanks for the tutorial on Acrobat downloading, I got your file and may I say that you have done a wonderful job! Just putting the book together represents A LOT OF WORK! Very professionally done.

I particularly liked your discussions and photos showing the crimping and soldering of connections and of various other things where a photo or drawing is worth a thousand words.

One of the biggest electrical problems I have run into when I have worked on cars is badly made connections of all sorts, but particularly crimped connections. I am sure you have seen them too, made with ordinary pliers, wire cutters, a hammer, visegrips, and the like. I attended a class years ago on wiring practices, and one of the discussions was about crimping and the need to use an honest-to-god crimping tool. There are many out there, and having one/some in our toolboxes is a worthwhile investment.

What was interesting to me about that discussion was that the presenter showed us test results between properly crimped connections and soldered and tho the soldered held a VERY slight edge, it was not a very significant one - IF THE PROPER CRIMPING TOOL HAD BEEN USED. He also showed us examples of poorly made joints of all sorts and badly soldered or badly crimped, they were notable for their poor performance.

I would imagine that your harness is going to be a very big improvement in reliability, much less performance. The wire you have chosen sounds better than what I have been using (it probably supercedes THHN - hell, its been 30 yrs since I started using that type - and is probably more flexible).

For anyone who can deal with unoriginal wiring, it looks like a great opportunity.
Bob Muenchausen

Dan

Got a chance to actually read all the way through last night. Excellent job! Any suggestions on tape or split loom for bundling and routing the wires?

Clifton

For those of us who are not up to date on inertia switches but do make occasional trips to the breakers where is the Taurus switch located in the car and what does it look like? Roughly what years should we be looking for?

Thanks in advance

Larry

69 C in restoration
Lawrence Hallanger

Bob and Larry,

I wrote an article on repairing or making wiring harnesses a few years ago for the Triumph club that you may find interesting. It covers wire wrap and soldered vs crimped joints, and offers a few other tips as well. I think I will add it to the Tech Tips page of the British V8 website.

It can be found at:

http://www.vtr.org/maintain/wiring-harnesses.html

Tape and split loom both work well, as long as you DON'T use electrical tape. Electrical tape goes on well, and looks good for a while. Over time, though, the tape will shrink, leaving the adhesive exposed where it will attract dirt and will slowly begin to look terrible. To say nothing of the mess if you have to handle the wire bundle. God forbid you should ever have to open it up and work on the wiring! There is a special wire wrap tape available from the sources listed in the booklet that works very well. It is non adhesive, but it does cling to itself. You might need to use a small amount of electrical tape to close off the loose ends of the wrap tape, or to seal off the open ends of the split loom, but use it sparingly.

Tape is almost impossible to use neatly if the wiring harness is still in the car, but if you take the loom out and then wrap it, it makes a very professional looking job. The downside to tape is the difficulty of making repairs or modifications later. if you have to split the tape to get to the wiring, it'll never look the same again - you'll always be able to see where the repair took place. It is a real pain as well, to have to open up a wrapped bundle to find the wires you want.

Split loom works as well, but it doesn't look as professional. Some people want the professional, or factory, look, while others prefer that it shows that you did it yourself. It's a personal preference call on that basis.

Split loom is a real pleasure to encounter if yoou have to make repairs or modifications. It's so easy to open up and find the wire you are looking for.

Personally, I use split loom in the trunk and under the hood, and nothing at all inside the car where the wiring will be hidden from view and protected from direct sunlight, grease, oil, etc.
Dan Masters

Larry, The switch is located in the trunk left side on most Tuarus, Tempo's and Thunderbirds from the late eighties to mid or late 90's. Perhaps other Fords have them in the same location. The is an access hole in the panel with some information about resetting the switch in event of failure. It has a neat bracket which you should also get, I reversed the bracket and mounted the switch on the right fenderwell of both my cars. Mine is connected in the white wires going to the fuel pump. I unplugged the fuel pump wire from the bullet connecter for white wires in the bundle of connecters on the right fenderwell plugged one wire into the bullet connecter and connected the other wire to the white fuel pump feed wire. You could also install it in the ground circuit as Dan's drawing shows and mount it in the trunk. I have a photo of an early switch from a Tempo and a photo showing where it's installed in my 74. Later cars had a switch that looked a little different but used the same mounting bracket. To test the switch shake or sling it and the ball will open the switch you can verify that that it opens with a meter set to measure resistance, it should read infinity, reset the switch and you shoul read 0 resistance.

To see the photos click on my Yahoo Photos link and click on the Fuel Pump Inertia album, my photos are all open to the public, no password is needed.
http://photos.yahoo.com/flash1929

Regards, Clifton
Clifton Gordon

This thread was discussed between 13/11/2002 and 15/11/2002

MG MGB Technical index

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