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MG MGB Technical - Multi-pole connector replacement

I'm fitting a new ignition switch to my '79 BGT. The new switch is complete with an original style 7-pin socket to connect to the plug on the dashboard loom. The loom plug was damaged some years ago (to get round this I put a temporary link in to bypass the faulty pin). I now need to replace the plug. Does anyone know of a source for this style plug/socket? If not, I'll have to replace them both with whatever's currently available.

The photo shows the socket attached to the ignition switch I've just removed, alongside a Tyko Mate-n-Lok socket which I suspect doesn't have the same current-carrying capacity.

Brian Shaw

Hiya.


It's a type of connector made by a company called Ripaults, they are available or if you get really stuck, sure i have one laying about I can send you.
SR Smith 1

Current carrying capacity for for the ignition switch on a 77 and later isn't an issue as both the ignition and the starter have relays, unless you have some high-current device on the accessories connection.

You should be able to get the pins out of the wire-side of the holder by sliding a close-fitting tube over the pins, and effect a repair by soldering.
Paul Hunt

Try Autosparks

http://www.autosparks.co.uk/index.php?cPath=94_735
Dave O'Neill2

Thanks all. I've ordered a new one from Autosparks.

I haven't any high-current items installed, just a radio.

I checked the wiring diagram for my car. The 12v+ feed to the ignition switch is a brown wire which, when the car is running, supplies the following:
Radio, indicators/hazards, heated rear window, heater fan, tacho, ignition relay, ignition coil (via ballast).

The brown wire attached to the new ignition switch I've bought is thinner than the others (strange, as the brown wire has to carry more current than any of the others). The wire size is 16/0.25 and insulation appears to be PVC (rather than thin-wall XLPE). The other wires are 16/0.30.
Brian Shaw

What diagram do you have Brian?

The Workshop Manual shows 77 models as having everything off the ignition relay, but my copy has no schematics for anything later.

Haynes has a schematic for 'later' models which shows the items you mention coming off the ignition switch as you say, but Haynes only has one schematic covering several Workshop Manual schematics so some differences between the years are ignored.

I know later models were wired as per Haynes, possibly because there was a problem with ignition relays sticking on, and that may have been retro-fitted to some 77 models when in for a service.

It's relatively easy to work out how it is wired - simply remove the white wire from the ignition relay and see if the engine starts and runs, and whether the tach, indicators work and the heater fan work or not.
Paul Hunt

Paul-

The wiring diagram I have is a copy from Haynes titled 'Late UK Market MGB from Haynes' which I tend to use as it's easier to follow than the Leyland diagram. My car was manufactured in Oct '78 and is described as a 1979 model.

When I've fitted the new multi-pole connector and ignition switch I'll check how the ignition relay is wired.
Brian Shaw

For some reason I read this as a 77 model ...
Paul Hunt

I've checked the ignition relay wiring and it's as shown on the Haynes diagram, so the ignition coil isn't switched by the ignition relay.

Paul, I've probably got the same factory workshop manual as yours (I bought it at the local BL dealers in 1980 - 'Repair Operation Manual 1978' part number AKM 4070). The diagram in it is 1977 UK spec, and it has BL drawing number 7NB007 (bottom RH corner). Sometime in the distant past I seem to have acquired the correct diagram for my car, and it appears to be photocopied from a BL manual. It is titled 'Wiring Diagram UK specification' but not dated. It has a BL drawing number 8NB045. Apart from the ignition relay wiring mod there are a few changes to wire colours, and an additional in-line fuse (ref 44a) which supplies hazards/indicators, heater fan motor, tacho, heated rear window.
Brian Shaw

Different to mine then, AKD 3529 15th edition, with number 86842 on the 77 wiring diagram. I'd like a copy of your 8NB045 if that's possible.
Paul Hunt

I don't know how accurate these are and most are for USA cars but a few at the bottom are for UK cars too

I don't know if the very last one might help (or hinder) but just in case - http://www.advanceautowire.com/mgb.pdf
Nigel Atkins

Paul - I've scanned the '79 diagram and produced a .pdf file, will this be ok?
I can forward it to you via the email link on mgb-stuff.
Brian Shaw

Thanks Brian, pdf received.
Paul Hunt

This thread was discussed between 01/06/2013 and 11/06/2013

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