Modern vehicles are rather difficult in that respect because 99% of the controls and hardware are all computer controlled and talk on the communications bus. Take a simple power window. From day one the electric power window has used a very simple system of polarity reversal. The switch gets power and ground and by reversing the way they connect to the motor it turns one direction or the other and the window goes up or down.
The simplest version has two wires to the switch, two wires to the motor. The reversal is done right in the socket that plugs onto the back of the switch.
These days that is all gone. Now the motor gets four or more wires to it, two power and two for the com line (in the more complex there are also monitor wiring to sense if the window is blocked or fully up/down). The switch gets power and com as well. Instead of the simple polarity reversal when you move the switch, a signal is sent to the Body Control Module. That signal is either a different voltage for up/down or a pulse that defines the same. The BCM gets the signal and determines you want the window down. It then activates the transistor output to the window module which activates the down control circuit and down goes the window. Door locks, sunroof, pretty much everything else in that vehicle works the same way. Take the "radio" as another one. Most are far more than just a radio these days. Many newer vehicle use them to program features in the vehicle and if they are removed or you try to replace them you can end up with a vehicle that does not even run because the security system does not see the radio on the network.
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Wednesday, June 13th, 2018 AT 12:34 PM
