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MG MGB Technical - Best pull-handle wiring diagram

I have to start labeling up a new harness for a very early B prior to installing it. Experience tells me that it's best to do this on the dining table with a good clear diagram that resembles the layout on the car. The Advance Wiring one has all the pretty colors, but the layout doesn't correspond to the physical loom. Does anyone have a recommendation - I have the workshop manual one too, just wondering if there is anything more user friendly before I start.
dominic clancy


The trouble you are facing is that the wiring diagrams are shown to simplify the tracing of circuits, while the loom is set up to route (in an occasionally convuluted fashion) circuits throughout the car. You have already identified the finest diagram I know of, the Advance Wiring set. You learn to compare a quality diagram with a harness very quickly with practice. It is a skill worth having.

You didn't ask, but I can tell you from experience that labeling a harness in advance is not really necessary. Although I do like to verify certain components using the harness prior to installation, the best course of action is as follows:

Double check the security of any crimped terminals. I once wired a car with a harness that had several terminals crimped to the PVC but not through to the wire. It made troubleshooting the eventual problems difficult.

Tin any bare wires with solder. Attach any missing bullets, I prefer soldering them on.

Lay the loom in the car as closely to its routing as possible. You will be amazed at how easy it is to wire the fuse terminal, generator, or other components because the proper color wires will land right next to the components. Refer to the Advance Wiring diagram to guide you.

Hook the 'battery' end of the harness to a battery charger set at 2 amps and check your circuits. When you make the final connection to the battery, use a 17 amp fuse between the battery feed and the wire for further testing. Remember the following:

Brown always hot
White hot when switched by ignition
Green hot when switched by ignition and it is fused
Blue headlamps (blue with white main, blue with red dipped)
red parking lamps and some accesories.

Striped wires are just designations of the above overall circuit codes.

Those codes have been used since very early in MG and British car history.

good luck,
Dave Braun


I got one from....

for my 1965 pull handle and find it a great help. I would highly recommend getting one.



C Briggs


Where did you get you loom from as the auto wire diagram was near spot on for my early 63 car ,the loom came from the wiring company in the uk.

What wires seem to be wrong?if its to do with the indicator/light switch on the floor its because the early switch isnt avail with the aluminium body and not flash on the stalk,it is now plastic body with flash so odd wire is wrong.

Ste Brown

Dominic - I believe that the wiring diagram in the shop manual is as close as you will get to being drawn as the harness is routed. Cheers - Dave
David DuBois

Thanks for the comments so far.

The loom came from Moss in the UK. Although the listing says "Complete Loom", it isn't complete. So far it is clear that the headlamp pigtails are missing, and all the instrument lighting fittings are missing - the loom just ends in a red and white cable with a bullet connector for these!. The only non standard colour in the wiring I have found so far is that one wire is green and brown instead of light green and brown. Also, even though I have also bought the additional loom for the OD, it is short of the cable to the OD solenoid itself, and unlike the rest of the loom, it's not cloth braided.

Can someone also tell me whether the ign and hi beam warning lights are supposed to have clawed / screw-in fittings, or are the wedge bulb connectors standard?

Also, what is the best way to drop the dash to rewire it (and is it easy enough to remove it to repaint it while I am at it?)


dominic clancy


The headlamp wire stops in the middle of the car and you buy new headlamp wires to attach to the loom as they are not classed as the loom.

The same is also on the instrument wiring which you use your own or buy new ones with the push in bulbs to match the others that are attached to the loom already as the screw in holders are not avail so these are the next best thing.

The loom from moss and anywhere else is classed as the main loom so anything attached to it is not supplied which also includes the overdrive and relay loom as they where always an extra.

This is the main reason why i got from the wiring company as they made all the loom for me together but i had to ring them about the relay loom as that wasnt included in the price and the horn wire as well for the second horn.

my web site is for wiring and piping pictures.

Ste Brown

Ste Brown

I have had my 3brg pull door handle car for over 40 years and I thoroughly enjoyed reading your entire restoration story. You have put a lot of effort into that well done. I certainly learned a lot.

Do you have the little bracket that goes from the rear generator bolt to the oil cooler pipe?

The original cotton covering on my loom is green. I am not sure if I have seen that on any other cars though.
Ian Buckley

No I didnt have the bracket as my car didnt have the oil cooler as standard and could never find a picture of the baracket.
If you could take a pic i would be very grateful.
My loom is yellow traced and wastold by the wiring company that it should have been white but it was definatly yellow under the dash un-sunbleached so i had it redone in yellow.
I wonder if it was a matter of when the looms were made they just run whatever colour they had in the machine.

Ste Brown


If you email me I can help with the bracket. Slight problem is that I am in Germany at the moment.


Ian Buckley

This picture (from Lee Miller) shows the clip/bracket from gen. to hose

DK McNeill

My beef is that the catalogue clearly says "complete loom", and it very clearly isn't, and there is no clarification at all that various bits are missing or have to be ordered on top. I can understand that the OD harness is extra (as OD was optional) but WTF with headlamp and sidelight wiring?. That was never optional! And why only part of the OD wiring in the OD harness, not all of it? Strangely enough, wiring for both horns is included.
dominic clancy


I can see your point to a certain extent but headlamps and side lamps are not the loom and never have been no matter who you talk to.
If you look at the pic on the web it shows that they are not there and it is a picture to cover all models so thats why the wire is there across the car for the brake switch on left hand drive cars.
As for the overdrive loom it will work with or without the relay and vacuum switch so that is why it is listed under part number 4 in the moss catalogue.
I dont understand why they list the pull handle cars as a full loom but 68 on as a main loom and a seperate rear loom.
I would ring them and complain that it is missleading and see what they can do about it.
The bulbs are 2.2watt bulbs so if you havent got any get them to put some in the parcel with the overdrive loom.

Ste Brown

Headlamps, parking/indicator lamps and rear lamps have tails or sub-harnesses that plug into the main and rear harnesses. The main harness should carry the wires for these (and horns, number plate lights etc.) to both sides of the grille and to both rear light clusters.

I've not looked at a very early B but the factory diagrams show the same for these as for later cars, that is a main harness and a rear harness. When reversing lights and OD were added these had their own sub-harnesses. Much later on there were also sub-harnesses for the dash.

I honestly don't think you need to label the wires beforehand, especially with the very basic wiring of the early cars, precisely because everything *is* colour-coded and is formed to drop the wires out of the harness close by whichever component they have to go to. There is very little scope for confusion if you connect the right coloured wires to the right component, the correct numbewred terminals, and connect colour to colour where bullet connectors are concerned.
Paul Hunt

This thread was discussed between 11/09/2009 and 14/09/2009

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