The smart is different to many cars which is what confused me for years.
The smart switches the earth to complete the circuit instead of switching the live.
So, what happens is, when you open the door, the SAM unit switches the earth so it is grounded.
This allows the voltage to flow from the live, through the light and out through the earth.
When you flick the switch to turn the lights on manually, it connects the permanent live to the permanent earth.
Here you can see I have used snap lock connections and tapped
into the permanent 12 volt and the switched earth.
After fitting my foot well LEDs, I ran the wires behind the dash and out of
the switch hole. LEDs only work with the correct polarity. I wired the LEDs
to the correct wires and used heat shrink to protect the connections and
stop any short circuits.
Push all the wiring back into the hole and check out the lights.
The LED strips I used where actually from Ikea (called Trettion), for £21 you get four 1 foot strips
and they are modular. You get the joining cables and a power converter, this can go in the bin.
These LEDs run off 12 volts so the converter is not needed. The LED strips have
connections at each end so you can daisy chain all 4 in a row if you wanted to do that.