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MG MGB Technical - Indicator switch wiring for Mk1

I just got a replacement indicator stalk switch for my 1963 B from the B hive and wired it in last night -- needless to say, I'm having bad results.

It looks pretty straightforward....unplug one wire at a time from the old switch, plug the new wire in, matching colors...not so easy for me i guess!

I have two extra wires from the switch that aren't used on the original switch; namely the blue/white wire for the high beams, and the ground.

Has anyone else used the aftermarket switch from Moss/B hive on a Mk 1 -- please let me know what I have foolishly done worng.

thanks,
Erik.
EMB Erik Brzoska

So what's the problem?
Paul Hunt

Erik

Its because the 63 switch would not flash from the switch but only from the floor.
The new switches flash from the switch so thats why the wires there.
On the 63 cars the cowl round the switch is just oval but on the later cars it also had a cutout as well for the switch flash.

Ste


Ste Brown

Eric - The blue/white wire is for flashing the high beams, a provision that wasn't on the original switches in NA spec cars(I wired that to the wipers so I can initiate a single swipe of the blades when driving in drizzles). Not sure what the extra black wire is used for. Cheers - Dave
David DuBois

I'm sorry...in my haste i completely overlooked the obvious -- what are the symptoms?

Nothing works -- no indicators at all.

Something simple, I'm sure...but i wanted to borach the subject to see if there were any "gotchas".

thanks for any and all help/responses,
erik.
EMB Erik Brzoska

The black wire is screwed to the steering column to earth it. If I remember rightly, the indicators are earthed through the switch and need the earth to work. Has the black wire got an eye on the end (a flat connector with a hole about 1/4" diameter)? This cable goes to the strap that holds the whole switch onto the outer column.

You can add an extra cable to the loom to connect the blue/white cable to the blue/white cable that goes to the headlights. You can now flash your headlights.

Mike

Mike Standring

Ah, just twigged. The early MGBs had a three-pin flasher unit, which is quite different to the later two-pin or the modern after-market three-pin.

There is a green feeding 12v to the flasher unit, and a green/brown or light-green/brown from it to the part of the flasher switch that connects to the lamps at the corners of the car on green/white and green/red wires. The third, light-green/purple wire goes to the two tell-tales, and the other sides of those go on light-green/blue and light-green/yellow wires to two more contacts on the flasher switch, which connects an earth to one side or the other depending on which way you move the switch. The eqarth is wired back via a bullet connector to a common earthing point on my schematic.

I wouldn't have thought that the repeater lamps on the dash would need to be working for the main lamps on the corners of the car to, for safety reasons, but I could be wrong.

With the ignition on you should have 12v on the green at the flasher, and the light-green/brown. When you operate the switch this should be extended onto the green/white or green/red wires to light the lamps immediately, then after a pause they should start flashing off-on-off-on (at least this is what happens on the later 2-pin and modern flashers). With no lighting or flashing either side check you have 12v on the light-green/brown at the switch with the indicator switch both operated and in its normal position.

As another test tap a 12v supply onto the green/white and green/red wires at the switch to check the indicators at the corners of the car light, then tap it on the common contact i.e. the light-green/brown wire and operate the switch first one way than the other to check the switch both sides.
Paul Hunt

This thread was discussed between 17/11/2009 and 18/11/2009

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