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MG MGB Technical - Ignition Switch Replacement

Greetings from Munich --,
has anyone ever replaced the ignition switch (and only the switch, not the complete lock)?
I cant quite figure out how this thing is attached to the lock - glued? Also, the part that's still in place has four pins, the switch I bought has 6 + 1 leads.
My MGB is a North American 1972 Model (#258067), but was rebuilt in Germany in the early 90s, sometimes with parts not exactly from the right period.
It seems that the wiring conforms (mostly) to the diagram pictured on page 193 of the Haynes repair manual. So my guess is that I can use the 6+1 switch and connect only those four contacts.
Any help greatly appreciated,
Christoph
CW Poschenrieder

That car *should* have six wires to the switch, or at least five it it picks up the earth/ground from the physical mounting. The switches were usually available separate from the lock assembly, attached with screws of some kind, maybe under a removable cap. I'm assuming you have brown (live all the time), white/green (accessories, live in accessories and run positions but not crank), white (ignition, live in run and crank) and white/red (starter, live in crank only) wires, and is those colours are on the switch itself just connect them colour for colour with the harness. If the colours are different you will have to test which wires are connected to which in each position of the switch and connect to the harness accordingly.

The additional wire was a purple/pink for the 'door open, keys in ignition' warning buzzer.

Take care with the conenctions, the brown wire is unfused and if it or any of the others short to metalwork it can damage the wiring.
Paul Hunt

Thank you; you're right, there are the colors you mention. The brown has two points on the switch that go into one thick brown, the pink-purple is in the bundle, but not attached to the switch, where there is an additional blue wire: This one I havent yet identified.
regards, CP
CW Poschenrieder

Are you sure it's blue? Could be black i.e. the ground for the 'key in' warning part of the switch. No blues in that area on any of my diagrams, although there was an additional slate (grey) for the anti-runon valve as part of the main switch on later models.
Paul Hunt

The ign switches in that period were a bag of snakes: not available, available as switches without locks or vice versa, required wiring alterations, etc. Given that your car is known to be a mishmash, you have to figure out function required and function supplied by the bits in hand.
Even worse that at least some of the switches/locks were German, so you may have something retrofitted that we've never seen here.

FRM
FR Millmore

Right -- baby blue, @ pin 5 of the switch. No grey though. I will attack the problem on Saturday and report back.
best, C
christoph poschenrieder

For the 72 model year the white/green accessories wire moved from terminal 4 to terminal 5, there being no terminal 4. But as FRM says and I have observed elsewhere suppliers and hence exact detail could change willy-nilly subject to strikes and cost.
Paul Hunt

It worked ... the old switch was full of a yellowish powder, the terminals quite corroded. I checked all wires beforehand for voltage at the three key positions. The old switch did not have the white-green, but a white-brown wire instead. It seems that the replacement switch is of a one-size-fits-all kind, with all its extra wires for buzzers and stuff.
thanks & cheers
C
christoph poschenrieder

This thread was discussed between 22/07/2009 and 26/07/2009

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