Keiranleigh Posted June 22, 2018 Report Share Posted June 22, 2018 Hello, I'm trying to get my head around how the cars interior light works there are three wires (brown white tracer, red, brown) red constant 12v, brown earth, brown white switching earth. Easy enough. (It only uses the brown if you manually move the switch on the unit). But how is this switching earth controlled because it has the dimming function (after 30s it drops from 12v over a period of 1s to 0v) at first I thought this was a capacitor but if you switch the earth to open circuit it can not discharge, can it? I first saw this- here (link attached) - about dimming lights. This all came about because I plan to install some LEDs in the foot wells and boot. When planning the circuit I wanted them to operate on the interior light aswell as a added switch. Easy enough but when investigating the switching earth I wondered is it ECU controlled and where do the wires run? Attached is the picture of the simplified wiring diagram. If it is ECU controlled would I get away with just adding diodes to protect the ECU? Thanks keiran Quote Link to comment Share on other sites More sharing options...
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