Morris Minor Owners Club

Just a suggestion Mike.
You have a permanent live feed at the ignition switch. Fit a piece of suitable cable from the same terminal across to the light switch. Remove the ignition fed wire currently powering your light switch and replace it with the new piece of wire. Take the removed ignition fed wire cut off exposed core and insulate the end of the wire, it will be an ignition controlled cable available for any future need.
Your permanent supply to ignition and light switch will now be as intended. Much easier than trying to trace the error.

Your permanent supply to ignition and light switch will now be as intended. Much easier than trying to trace the error.

Hi Bill,
My current thought, having seen both ends of the loom I have fitted, is that this 'error' may even be in the way the loom is configured.
A spare ignition live, sealed up for now, may prove, as you say, to be useful in the future.
However I was advised earlier by Stephen:

I think the main reason why you should not do this is that with the headlights on there is a lot of current going through the ignition switch. It is just not rated to handle this current.
From what I can find, the Lucas 31973K (the original part number from my 1969) is rated at 5 amps on the ignition circuit which is pretty close to what the coil and the fuel pump draw. In other words, the ignition switch is already almost fully loaded. The sealed beam headlights (as an example) are 65w/55w. So with the headlights on dipped that is 110w at 12 volts =9.17 amps. Far too much current for the poor ignition switch. It will overheat and melt!
Obviously your car is earlier but still the ignition switch is not meant to handle that current.

Ii's advice that I intend to heed, so the feeds are going to be separate.
Best wishes,
Mike.

jagnut66 wrote: ↑Sat Aug 22, 2026 11:49 am

Your permanent supply to ignition and light switch will now be as intended. Much easier than trying to trace the error.

Hi Bill,
My current thought, having seen both ends of the loom I have fitted, is that this 'error' may even be in the way the loom is configured.
A spare ignition live, sealed up for now, may prove, as you say, to be useful in the future.
However I was advised earlier by Stephen:

I think the main reason why you should not do this is that with the headlights on there is a lot of current going through the ignition switch. It is just not rated to handle this current.
From what I can find, the Lucas 31973K (the original part number from my 1969) is rated at 5 amps on the ignition circuit which is pretty close to what the coil and the fuel pump draw. In other words, the ignition switch is already almost fully loaded. The sealed beam headlights (as an example) are 65w/55w. So with the headlights on dipped that is 110w at 12 volts =9.17 amps. Far too much current for the poor ignition switch. It will overheat and melt!
Obviously your car is earlier but still the ignition switch is not meant to handle that current.

Ii's advice that I intend to heed, so the feeds are going to be separate.
Best wishes,
Mike.

What I meant was current going through the switch. If you are just using the switch as a junction before the switch I can't see a problem.


Stephen

As Stephen just explained if you follow my suggestion it a permanent power supply to two separate switches and the cable size is designed to carry the load. Each of the switches will be switching the load they were designed for and it will be wired the same as the original diagram, apart from the one spare unused wire.
In the end its your car so you have to do what you feel best with.
My comments are only advice trying to give you a simple solution. It sometimes seems obvious when you have years of experience with vehicle electrics but I understand it can be worrying if its not your field.
Good luck with whichever way you choose.

On your photo, I would say that the connections to the RB106 are correct.
However, totally unrelated to your problem, the connections at the bottom Fuse are reversed.
It doesn't matter at the top fuse as there is only one terminal screw either side.
But at the bottom fuse the 3 white wires should be at the single screw on the left side and the 3 green wires should be split between the 2 terminals connected by the link. Thus sharing the load a little. At the moment the lowest terminal is Bare, because the input and output are reversed. But back to your problem, I refer you back to my earlier statement that the Brown/blue from the RB106 connects to the Light Sw input terminal and then to the Ign Sw.
As basic as that.

The concerns you are expressing about separate supplies are irrelevant in electrical terms, the supply to the Ign Sw and the Lights Sw are both direct from the battery via A1 on the Regulator. Whether there are 2 or 22 switches connected to a single wire from the 'supply', in this case terminal A1 on the Regulator, it makes no difference, the current rating of the cable being of sufficient rating.

The manual shows it from A1 to Light Sw to Ign Sw .

You appear to have A1 to Ign Sw but then only 'after' the ign sw it goes to the Lights.
To correct it as per the manual you need to put the cable from A1 onto the Light Sw input and then bridge it to the Ign.
. .
The quickest fix is to just move the Brown/blue from the Ign output to partner the Brown/blue that is already there...

But at the bottom fuse the 3 white wires should be at the single screw on the left side and the 3 green wires should be split between the 2 terminals connected by the link. Thus sharing the load a little. At the moment the lowest terminal is Bare, because the input and output are reversed.

I didn't realise, everything seems to work okay, I must have misread the diagram when connecting them up......

As Stephen just explained if you follow my suggestion it a permanent power supply to two separate switches and the cable size is designed to carry the load. Each of the switches will be switching the load they were designed for and it will be wired the same as the original diagram, apart from the one spare unused wire.

The concerns you are expressing about separate supplies are irrelevant in electrical terms, the supply to the Ign Sw and the Lights Sw are both direct from the battery via A1 on the Regulator. Whether there are 2 or 22 switches connected to a single wire from the 'supply', in this case terminal A1 on the Regulator, it makes no difference, the current rating of the cable being of sufficient rating.

Noted.
Thanks and best wishes,
Mike.