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MG MGB Technical - Ignition Switch Wires

I am replacing the ignition switch on my '72B. The replacement switch has 4 wires, white, brown, brown/white and a white/red stripe. The unit in the car has a purple/white that plugs in under the switch, & brown, white, white/red and a white/green that was not connected. Can I ignore the purple, and just connect the 3 on the new switch that were in common with the old? What was the purple/white wire for?
Joe Dufresne

Joe, take a look at the diagrams here:
http://www.advanceautowire.com/mgb.pdf

Check that you have the correct switch for year and model of your car. Bear in mind the car wiring may have been modified by a previous owner, also the switch you have on the car may not be the original one.

Purple/white seems an unusual colour for ignition switch wiring - have a close look at this - could it be purple/pink?

Brian Shaw

Anything purple on UK spec cars is always live, irrespective of the ignition switch AND when the key is out. This powers cigar lighter, courtesy lights and horn. Most replacement switches are 'borrowed", usually from LR, improbably has a use on a Range Rover! If you put a continuity tester on the wires you might find the purple is in permanent circuit with the brown.
Allan Reeling

Have a look here http://www.mgb-stuff.org.uk/isw.htm

North American had a purple/pink on the ignition switch which is for the 'key in' buzzer, I doubt you will miss that with the new switch.

You need to test the wires for connectivity in each position of the switch to work out what goes where. If white/red is connected to brown in the crank position, then brown/white is *probably* in place of green/white which should be connected to brown in the first on position of the switch when the white is *not* connected to brown, also in the second on position of the switch where white is also connected to brown, but isolated in the crank position.
Paul Hunt

Just went through this this weekend -

The brown solid fits to the brown solid for power. The white w/red goes white with red, to trip the starter solenoid.

The white goes into a 4-way bullet connector, and the brown with white goes to the green with white.

The white-green is the wipers and blower - do those work, or if not perhaps you now know why.

Unfortunately in sorting this out I may have fried my tach, which will be in another thread.

Steve
SS Aichele

Hello, Further to this thread. How do you remove the wires from the switch? Is it a plug or do you remove them individually?

Thanks
John Dale
John C. Dale

John - depends what year your car is.
Check these:

Late 1970's: http://www.ebay.co.uk/itm/MG-NEW-MGB-1974-ON-STEERING-LOCK-IGNITION-SWITCH-BHM-7144-/380662929531?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item58a147587b#ht_1255wt_720

Early 70's: http://www.ebay.co.uk/itm/MG-NEW-MGB-71-74-ON-STEERING-LOCK-IGNITION-SWITCH-BHA5215-BMX2259-/310693880347?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item4856cc621b#ht_1200wt_720

1960's: http://www.ebay.co.uk/itm/MGB-IGNITION-SWITCH-ASSEMBLY-/380600249143?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item589d8aeb37#ht_119wt_720

Mine is a late 70's which has its own loom attached, and is soldered to the switch terminals.
Brian Shaw

This thread was discussed between 12/06/2013 and 24/06/2013

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