Hello all,

I am planning to install 2 footwell led lights into my car.

The idea is to have the white footwell serves as welcome light that goes on and off with the interior lighting, and the RGB footwell has the same function but there is an additional switch on the driver side panel to wire it up with constant ground such that I can keep it on while driving if needed.


The design shown above may be problematic as I believe all interior lights and the white footwell would also turn on when the switch is closed.

My thought to solve this is to put a diode between the RGB footwell and the M14 Red wire such that current cannot flow from the Red wire to the switched ground.

I only have basic electronic knowledge from high school so I am not sure if that will work if a diode is placed on the ground section. Don't wanna try it on my car to avoid causing any problem to the BCM.

Could someone please help and advise?

 

A lot of this is going to depend on if the door switches are actually part of the lighting circuit or just a signal to the BCM to say the doors are open. If the switches are directly connected to the lights then your second drawing should work just fine.

One thing you don't show is any current limiting resistors on the LEDs, but if you are using standard automotive type lights (panel indicators and the like) then they aren't needed.

What are the details of the car? If you're in the Americas somewhere Mitchel DIY is a good source for wiring diagrams and electrical details, but it will cost a little.

Unfortunately when it comes to automotive stuff a lot of the times we can only make educated guesses. It is hard to find accurate and free information online to help guide people in their projects.

 

1N4002 diode should stop any backflow and keep the LEDs working right. Make sure it’s rated for at least 5A (10A is even better) to avoid overheating.