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MG MGB Technical - '63 B Headlight Harness Routing

Hi again,

The current headlight harness (if you can call it that) for my '63 B kind of drapes under the front of the car, behind the valance. It is an absolute mess with wire ties, electrical tape, and non-original wires.

Anyway, I believe it should be routed from fender to fender, on the underside of the panel with the bonnet catch (is that called the slam panel?), and it passes through holes on the inner fenders to the headlight buckets, etc.?

I will be installing a new headlight/horn harness. Would someone be so kind as to post or email me a sketch or photo of how the harness routes from fender to fender? I also have no clue where the ground ought to be.

vanhookvintage@epix.net

Thanks in advance,
Greg
Greg Van Hook

My 1965 has the harness going through the far right side of the radiator diaphragm then routing under the hood latch panel secured by cable clamps that look to be factory. The wiring to the signals and lamps exit through grommets in the inner fenders. The ground for this is to a screw holding a cable clamp just forward of the fuse box.

I've got a big nest of Lucas bullet connectors mid-point under the latch panel about center. I don't think this is original as it is not on the diagrams and shouldn't be for original equipment. I have a spare original horn harness likely the result of splicing pieces together. That would explain the connectors.

It's really hard to photo this as most is hidden.
Robert McCoy

I believe that the "nest" of bullet connectors, midway under the latch or "slam" panel is correct as the same set up is on our 66 MGB an when I was collecting parts cars, all had the same nest. That nest is also part of the replacement harness that I got when restoring the MGB.

Greg, all of the ground points need particular attention to insure a secure and long lasting ground. See the article, Electrical Connection Preparation in the Other Tech Articles on my web site at: http://homepages.donobi.net/sufuelpumps/ for information on how to insure that you have a good ground connection. Cheers - Dave
David DuBois

Greg

Here are a couple of pictures that might help - the nest of connectors is correct!

John

John Minchin

And here's the other

John Minchin

Dave,

I printed your article and already cleaned up a couple of grounds.

John, thanks a lot for the photos. Very helpful. On the first one, do I see the ground wire going to the bolt in the foreground?

I discovered last night that my main light switch is bad. I disconnected the wires and jumped the red and brown, and the map light worked. Then walked over to my workbench and saw, lo' and behold, the tail lights and parking lights were on! So, I jumped the brown, red, and blue, and the headlights came on!!!!!!! Even the flasher and new dip switch work!!!!!!!

But the insulation on the red wire to the panel light light switch was sort of melted at one time, and wrapped with electrical tape, and the panel lights don't work. Not sure what that's about.........

Gotta say, the headlight harness and dip switch harness I got from British Wire are very well made, absolutely first class, and I highly recommend them - good customer service, too. Ask for Josh.

Thanks,
Greg
Greg Van Hook

Be careful with that panel dimmer. The PO had allowed the dimmer rheostat to rotate in the panel shorting out the feed wire. That burned the wire back into the harness (the standard fuse is not going to protect a wire that size). I had to run a new wire to replace it.

Make sure the dimmer is securely tightened.
Robert McCoy

Greg
No the wire isn't grounded there. It probably wouldn't hurt to have an extra ground near the front (the rear wiring has a ground attached to the body near the boot(trunk) latch)

I can't remember how far away the closest attachement of the black wire to the body is.
John
John Minchin

I think it could well be by the right-hand headlight on 62-64 cars as they are the only things grounded at that point. 64-68 share the headlight grounding point with lots of things including the control box so I think it is likely to be closer to that. 69 and later share it just with the starter relay and it is by the fusebox, on at least some of those years.

Given the relatively heavy gauge of the wires feeding 12v out to the lights it comes as some surprise to find the earth return is standard gauge. Even more surprising on later cars with electric cooling fans as they use the same puny ground wire! I added local grounds to each of my cooling fan mounting brackets, and even after having the first one connected in parallel with the original wire I still got a noticeable increase in fan speed when I added a third ground at the second fan. The extra grounds are benefiting my headlights as well, of course.
Paul Hunt

This thread was discussed between 02/04/2009 and 08/04/2009

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