MGB & GT Forum

Hi Folks, I need a new wiring harness.....do I dare try to install it myself? I will tell you I am a neophyte in all things concerning cars, but I love my '76 B. I am ready to be back on the road. I will bite the bullet and take it to the shop if needs be. Just wondering...


Anthony

Do it. If in doubt, cut the old wires off, leaving the connectors. Then match the old and new colors one at a time.

It's not that big of a thing.

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Wayne Sanders
Rose Lodge, OR
(TD 4288)

"I don't care to belong to any club that accepts people like me"-joined Willamette Valley Club in 2011

79/65 MGB - Carmine- V-6 - T-5

This car is now very nearly completely done. Sure to find something else, but not now.........And 12 years later, I'm starting to fix things that were new when we built the car. It's pretty well de-bugged!

Many do it
a good schematic
a multimeter
a test battery and test lamp
Companies sell oe style or you can install modern upgraded both are color coded and come with instructions
http://www.advanceautowire.com/
http://www.advanceautowire.com/mgb.pdf
http://www.britishwiring.com/MGB-s/16.htm

Plenty of help and tips here on the forum

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LNDRVR4X4.COM
Home of Project "INCARN8'


1957 Series 1 Land Rover electric VEHICLE CONVERSION

FIXITUPCHAP.COM
FIXITUPCHAP INCORPORATED

RD3 Radar/ Electronic Warfare Technician
VIETNAM 1969-1972

Study the schematic first, then go out to you car and assess the situation. Wiring on these cars is very simple and if you go thru it connector by connector you shouldn't have a problem. The most difficult will be getting to the stuff behind the dash.

I'm no electrical expert, but I installed a harness in an MGA. If I can do it, anybody can. The (dumb) previous owner of my GT had some fairly weird ideas of how wiring should be done. I've spend a considerable amount of time tracing his extra wires and undoing what he's done. I would have rather installed a new harness.

Anthony,
Go for it. Getting a new harness is very doable, and as Dave says, if I can do it, you can.
You don't mention which one so I assume all, but there are three main harnesses (at least on my 73B): rear harness, engine and into the dash, and then a small dash loom for main lights and the rheostat.
Electrical is not my strong point, but we learn from these things. Fishing the wires through the holes with grommets is a challenge, but not impossible.
I've been very happy with www.Britishwiring.com - I'm doing the whole car.
Key is, go to Walmart or somewhere and get some sticker labels, and label every connection as you take it off. Take pictures.
Then, once you pull the old harness, lay it out on the floor side-by-side with the new one, and label the new connections if you think it will help.
Peace of mind with new wiring according to spec is a good thing as old as those wires are.
Good luck!

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Dan Ray
1973 Blaze Red MGB "Punkin"
2011 Shadow Blue VW GTI
2006 Black Ford F150 FX4
http://www.mgexp.com/journal/GunnDan

Suffolk, VA

Dan's got it. Replace it with an OE harness from British Wiring, take your time, be patient and it will be easier than you think. You should get a meter just for the fun of it and you'll learn to use it, too

When you have everything in and wired up, use nothing larger than a 10amp battery charger to make your first tests. That's enough current to run everything but the starter but not enough to immediately slag the new harness if you have something wrong. Use a charger with an ammeter built in so you can see if it pegs.

Go for it!

I have had great luck with my Sparks wiring harness. They make them for Moss. I enlarged my wiring diagram to 24 X 36 poster size and hung it on the all beside the engine bay. Do the engine bay first its easier then under the dash and the rear. Takes about 6.2 beers to do it.

You will do a far better job than the shop. For some strange reason, most mechanics don't understand electricity. Some know they don;t, some think the do, but evidence in cars proves otherwise.

With all new, you have a great advantage to add grease inside all the plugs. Then they will last almost forever. Get all new grommets for the firewall and other places. It will make the job much easier.

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Cogito ergo sum periculoso

I am just finishing up installing a new harness in my '77B. I am not overly mechanical and have minimal elctrical experience and have found this project to be very straight forward. Unless you have some very specific needs, I would stick to the stock harness. I am not the greatest at understanding wiring diagrams. Having the stock harness with the various connections terminating at specific points makes it easier to make sense of the diagram.

Dan hit it on the head takes lots of pictures, especially of how the harness is routed. I referred back to my old harness multiple times and the labels attached to the connectors. Be picky on how you label the connections and the type of maker used. My labels started falling off and the ink smeared due to all of the oil, making them hard to read.

Good luck.

Consider adding fusible links or inline fuses to the lines that come off the battery (starter post), relays on the light and horn lines, and especially adding a starter relay if your car does not have one. Purpose: brighter lights, louder horn, less wear (arcing and pitting) of dash switches, and less risk of electrical fires.

Thanks for all the encouragement! I will do it. I am ordering the harness today. I will keep you posted.

Anthony.

Hi, Anthony -

Good Man!

My advice is to put the car up on jack stands before you start work, and roll around underneath with a creeper. Get lots of pictures of how the cable passes through the cross members, and how the metal clamps under the right hand seat fit. Look for the screw attachments.

Then look on the inside right engine well noting how the wires come through the firewall. Also, see how the individual wires pass through the body into the lighting components. Get some pictures, and put them in some order that you plan to reassemble.

I put my '72 together from a bare hull and boxes of parts, so it's not really too big of a deal. Everything on mine WORKS!

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Jim K is a grease-stained wretch

Why do you think you need new harness ?

Other then a burn up there are few reasons for going that far.

X2 unless there was a fire or meltdown these harnesses are pretty resilient with just a clean up of the connectors or replacement of the corroded ones. When I got my car the PDO's made all kinds of "upgrade" mods to various connectors and lots of lights and switches didn't work as they should. A few crimped on bullets and new connectors, cleaned up or replaced switches and removal of all their mods and everything works as it should. Now if you find the wiring in the harness brittle and cracking then go for it otherwise through such an expense and undertaking for just a few bad connections. IMHO

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jb

Too soon we get old, too late we get smart!

My harness did not experience a fire, but I replaced anyways. It was hacked in to in several spots and many of the wires were cracked as illustrated in the picture below. My concern was that if this is what I could find what was lurking that I did not see. As expressed in this thread, this is not that hard of a project. If you are OK with spending the money, I would go for it, great piece of mind.