Map Light Question

[Philk]

Hi, as per other posts, I'm currently working through the wiring of my S1 OTS, fixing issues as I go. I have hit a (hopefully small) brick wall with, of all things, the map light. It works correctly when either of the doors are opened but does not operate from the switch on the dashboard. I have removed the switch and, using a test meter, can confirm that current does pass through it when it is switched on. On the car itself, there is simply a purple/white cable to one terminal and two black (earth) cables from the other.

Should the map light work with the ignition off or on? It is difficult for me to trace where the purple/white cable goes to since it disappears straight into the harness!

Many thanks!

[cactusman]

Purple/white from the bulb goes to both door switches and to the purple/ white at the switch. Other side of the switch goes to ground. Switch works irrespective of ignition. Check there is continuity from either door switch wire to the purple/white at the switch. Somewhere in the fuse area there is a bullet where four purple/white wires join....

[Philk]

Purple/white from the bulb goes to both door switches and to the purple/ white at the switch. Other side of the switch goes to ground. Switch works irrespective of ignition. Check there is continuity from either door switch wire to the purple/white at the switch. Somewhere in the fuse area there is a bullet where four purple/white wires join....

Hugely useful to know that the Map switch works irrespective of ignition. Thank you for that. I've not found the point where all four wires meet (I believe this is buried in the harness since the purple and purple/white wires to the map light itself disappear into a covered part of the harness adjacent to the ventilation pipe. The purple/white wire that goes into the switch emerges from the harness).

What I need to check (somehow) is whether current is getting to the switch. I suspect it is not (which may prove troublesome to locate).

[MarekH]

With the battery disconnected:-

Check continuity of purple/white at the switch with purple white at the door.
Check continuity of black wire at the switch to the chassis.

With the switch on, check continuity of purple whitre to chassis.

With the battery connected, if the switch is off and the doors closed, you should have 12v on all of the purple white wires. Once a door is opened or the switch is pressed, you should have 0v on the purple white wire.

Basically, the purple/white is the first half of the earthing side of the circuit. If there were any logic in the Lucas wiring it really ought to be black/purple colour if you think about it.

kind regards
Marek

[cactusman]

Ground the purple/white wire at the switch. If the light comes on it connects to the bulb. If not there is a break somewhere. Pretty certain there is a bullet joint somewhere where all four purple/whites join.