So, OK... you got me - this isn't strictly Arduino related!
However, I have recently bought a new car, and part of the tinkering I am undertaking is the following. I want to make the sidelights come on when the vehicle unlocks / when a door is opened. Fortunately there is already an interior light circuit to take a tap off. Unfortunately, the sidelight switch is ECU controlled and seems to use a 1.65V control line to sense the switch position. I have already tried shorting the red and grey wires (see below) and it produces the desired result - the sidelights come on, and no magic smoke escapes! Also on the downside, the interior lights are on a negative fader switch. I could realistically just pop in a relay to do the job, but due to slightly limited space and extremely low currents, I am trying to do it with a couple of TO-92 Transistors. However all the BJT's I have in stock have a 5Veb maximum, so trying to use a 12v range to switch them won't go to well.
Esentially - will the below (simplified) circuit become so bloated with protection components that a small relay would be a better plan?!