As usual I'm having a little trouble figuring out electrical goings on.

I've finally worked out how to wire in a bulb to show the door open light on the dash (just have to actually do it) by tapping in to a wire that runs up the off side A Pillar to the interior light, but on the back of that I'm trying to get door puddle lamps running on each door via the door open switches rather than all off of the interior light directly.

As far as I can determine the door switch grounds out a circuit enabling the interior lamp to illuminate (via some cpu according to the 323 Haynes manual I have, page 12.36), so figured if I just stick the puddle lamp in line with the door switch it should just be part of the circuit, simplesss.... or not.

I've got the wire to the door switch (Black & Red from the bottom front of the drivers footwell fuse box), split it and put a puddle light from a pre-Ford BA directly in line (just to test it). Now, the puddle lamp lights fine but the interior lamp is barely on. The two bulbs are 8w and 3.2w.

Thinking maybe there isn't enough power going through the circuit I swapped the bulb in the puddle lamp for an LED one (which are meant to use bugger all power) from my front side lights (both are capless wedge type bulbs). This time the puddle lamp shines brightly but not even a glimmer from the interior bulb.

So simple diagrams for what I'm doing:

Stock wiring:



With Puddle Lamp:



With Puddle Lamp & LED Bulb



So, what is going on? Would changing the interior festoon bulb to an LED one help? Do I need to source another 12v live and use the switch as a ground only? Or is this a tree not worth barking up?

Jon

Likewise water, the electricity follows the path of least resistance.
You are stealing the power of the interior bulbs circuit.
Try to connect it in other way, or just make new circuit with new feed for it.

Edit: You may say reducing not stealing.. it's the same..

just fit a push-to-break push button switch in the door jam near to the door hinges then run a +12 to it via the harness cover that is already going to the door, other side of the switch goes to the bulb/led and then ground the light to the door. You may have to tinker with the switch position to make sure the switch is depressed when the door closes. that way you'll only have 1 wire from cabin to door to fit, everything else is behind the door panel.

I've been reading a VW Transporter forum and they've done it by tapping in to the live for the electric window motor, to the bulb and then down to the door open switch, so the bulb draws power that way when the door is opened.

I'm guessing the door switch line is normally just a low power trigger for the CPU and not directly linked to the interior light itself?

Would that work in this scenario or would power be likely to run back up the line to the CPU? Don't really fancy frying that bit tbh!!

It shouldn't do damage to the ECU..
I believe that the circuit doesn't have anything to do with ecu.It has direct + from a relay wich is triggered by the key.It has its own electric borad inside and it's completely independent.
I used the + to make the green led backlight so it should do the trick.
BUT only if you turn the key.. or it was the front light switch??
I did my door lights with 2 wires, got the signal from the ceiling light cloned the + and - and made a whlole new circuit for all 4 doors..
I think that is the best way to go..
Everything is LED so the fuses are OK with the power drawn.
As i said before, in your case you put the 2 lights in series but you haven't tried parallel.If you put them parallel both will light up as expected.

Edit: in the first part i'm commenting power from the electric windows buttons.

Finally got my multimeter out last night to check things over. The line is drawing about 8 watts so enough for the overhead bulb but add anything else in a there's just not enough juice.

Think I'm going to try an LED cabin light and door light and see how that goes, if not I'll try tapping in to the electric window motor supply and earth via the door switch.

I really want it to be door specific rather than they all come on when you open any door, though I may have to fall back on that at worst.

Will let you know how I get on and cheers for the advice

Jon