need help with some electrical set up
 

got a 1974 911 s that i want to install some LED light on the inside here is what i wan to achieve than when the doors open and the dome light turn on also turn on the LED on the inside here is where come complicated i want also to turn on the LED light by itself by a switch on the inside but just the light not the dome lights, someone said me to put a relay but what kind of relay and how i can connected it. any help or opinions will be greatful

Tap the trunk light source and then fish it into the cab via the passenger side vent open port.

I placed a LED strip under the knee pads and when I open the door it illuminates. I can turn off the dome light at will so only the under dash lights up.

Hope that gives you a lead?

P.S. Welcome Aboard!

You could use two diodes, one diode for the dome source and the other diode for the switch source. The source connects to the anode of the diode. The two cathodes are tied together and connect to the LED load. The diodes will drop a little less than a volt, so make sure your LED’s will function OK with this reduced voltage.

you would have to connect your LED light after the switch in the door but you would have to install a diode in line with the wire from the door switch to the LED.
then you would have to connect your LED switch between the diode and the LED. the diode blocks the voltage from going back and turning on the dome light.

the cathode (the | side) needs to be connected to the LED to block current flow back to the dome light