Thread: Four pin ignition switch Series 2A

I'm guessing STA is for ''start'' or crank.

A new genuine Lucas Ignition switch for a IIa should look like this with the numbering - Original factory ones might be different. I'm seeing a lot of difference in some 1972 OE and 2025 OEM parts.

IMG_4653a.jpg


The switch mapping for the pins:
1. Power in
2. Ignition and switched power
3. Starter
4. Accessories - this might have no wires connected to it.

IMG_4651a.jpg

Sometime in the next week I'll upload a Youtube on how I repaired all of the wiring on my IIa. Almost nothing worked at the start.

Hello RandLover,

Yes, some further digging online - while I waited for my photograph to travel from my mobile phone to my computer via the internet - found a 4 posted 'universal' ignition switch that was labelled. ST is as you posted for START.

A photograph borrowed from the internet ... accessed 5th of July 2025 from Amazon.com is correctly labelled. So no Earth wire.

One of the looms I found is out of a Series III Ex-Army. It has a wire wire from the IGN (Ignition) post that connects to at least four other white wires. Two of these link up to various gauge cluster bulbs
At the BAT (Battery) terminal there is a brown wire that connects to at least three other brown wires. One of these brown wires goes to the lowest terminal of the Test Lamp on the instrument cluster. A second brown wire leads to the fuse box under the steering column. The one brown wire was cut off - I think this would have originally led to the positive battery post.

There was no wires connected to the ACC (Accessories)

A green wire was connected to the STA (Start) post. However, it was cut off and not connected to anything. I presume this wire led to the starter motor.

Does this sound correct?

Oh, The photograph taken of the ignition switch has still not come through. All of its wire were cut off at 5 or so centimetres - so I am relying on the later Series 3 layout for some idea of what wire went where. Both the Series 2A and the Series III have the same Made in the USA four post ignition switch. Same layout as the Amazon one in the attached photograph

Kind regards
Lionel

The factory wire colours might depend on what hour of the day the vehicle was manufactured. Some of mine were different to that stated in the wire diagram.

The wire to Battery should ultimately go to battery via a regulator block, but it may pick up that power from a fuse block - which might explain multiple wires to it. There will also be a wire that leads of it which powers the horn & test lamp sockets and to the lights switch which powers the dash lights, F&R parking lights and head lights.

The wire to the IGN will go on to power the ignition, fuel pump, dash gauges, stop lights, windscreen wipers and the blinkers

The wire to the Starter should only be one wire to the starter motor solinoid

ACC will probably have no wires to it.

You can use the above info to test your wiring - if you connect it you can probably see whats going on... or melt something.

Hello Slunnie,

Thank you for your reply. It would be great to see your YouTube clip.

At the moment I just want to test sort out the ignition switch while the engine is still in position to see if I can get the engine started. If the motor is a good one then it will be transplanted into a Series III all civilian 109 ute which has a very tired and worn out 2.25 litre diesel - all original diesel. The donor is a 2.25 diesel that I suspect was a replacement years ago for a 2A 2.25 litre petrol motor. I will be wiring up a temporary glow-plug circuit for the 2A.

I have not checked the engine serial number in the 2A to determine what model it was from.

Kind regards
Lionel

Oh, its a diesel!

Pin4 (ACC) should be connected to the glow plug circuit.

I wonder if that is a diesel specific switch, as the one I have maintains power to ACC when the car is running. I would expect the diesel doesn't want that to happen.

I'll post up when the YT is released.

As Slunnie says the STA wire should go to the starter solenoid, so as you are only testing you don't have to run the green wire, you could just short the starter solenoid terminals with an old screwdriver to get it to crank.