Hello all, I'm hoping someone can help.

I've just bought a 1970 XJ6 series 1 manual with overdrive.

Just below the gear selector, there are two lights: one green and one yellow.

I initially thought that these were standard factory-fitted lights, but looking at multiple photos online, it seems they're not present on other similar cars.

When the overdrive is engaged on the gear stick, the green light turns on. When overdrive is disengaged, the light remains off.

I've been wondering what the adjacent yellow light is associated with, until today.

I discovered that there's a metal "on/off" switch under the dashboard by the bonnet release. When this switch is flicked on, the yellow light comes on.

My question is that I have absolutely no idea what it does, and because these two lights don't seem to be factory standard, I'm not sure what this switch under the dashboard does.

I'm hoping someone has some suggestion?

The light circled blue is the overdrive engagement light. The light circled yellow is the light that engaged when the mysterious switch is engaged.

The mysterious switch, located by the bonnet release