Originally Posted by Shude
OP: I take it your hand-drawn diagram for the sidelights is front only? Are the rear lamps the same diagram? Could any components be shared?
EDIT: forgot to add, logically does this circuit also turn the sidelights on when the car door is opened with the ignition off? Also I suppose if you are sitting in the car with the ignition off and then turn on the interior lights with the button on the dome light!
when you scotch lock into the side light circuit the 2 wires are lift front and rear and right front and rear lights.
Sharing components can cause feed back issues as your connecting circuits together that normally are not.
But funny you should ask this question as yesterday a friend asked if it could wire this up in his E46 M3 and with that all 4 corners (sidelights) are wire separately so doing it how i wired the ML i would have needed 4 of the 5 pin relays i didnt need a 4 pin relay as like most cars (NOT AN ML...) the interior light is switched power not switch earth (like on the ML) so i had a think about it and instead i did the whole install with just one 5 pin relay and all i did to stop feed back issues is fit 1Amp diodes in the 4 wires that feed the side light circuits (FL,FR,RL,RR) so if i was to do an ML again i would do this the same way you would still need the 4 pin relay that send a switched power fromt the interior light but the 2 5 pin relays can be replaced with 1 and just cut and fit the 2 diodes in the 2 wires that you scotch lock into the side light circuit, the diodes have to be wired in one direction as they will only let the power flow in one direction this is how you stop the back feed problem (far simpler)
Here are the diodes i used:
1A Glass Passivated Rectifiers : Diodes : Maplin Electronics
As for when the lights are activated yes when you open the doors and if the ignition is off and you turn the dome light on it will turn the sidelights on you can get round this by using the lights on the bottom of the mirror if you wanted to sit in the car and read without all the lights on.
I think i will re-wire mine and use diodes as it makes for a cleaner install so i will take pics then and do a good write up with wiring diagram