Well to know if they will work or not, you will need to identify a few things, are the switches you're replacing of the same type? If you're just replacing an ON/OFF switch you should be fine, however if the switch has more positions(FORWARD/OFF/BACKWARD, OFF/SLOW/FAST, etc.) it will not work. As to whether they will actually fit into the space you intend for them, I can't really help you there. These won't work well if you want to fit them onto a curved panel, they're meant to be mounted to a flat surface. Also a mounting problem, you will need to be able to remove the panel your putting them in, because these get mounted from the back. Additionally, you will need quite a bit of space behind the panel because of the large bulk of these switches. More than likely, you will need to fabricate a new panel with a flat surface for mounting, but comes forward enough for the switches to clear all the stuff behind it. Compared to the size limitations, wiring it up would be easy. On the switch I received, the markings telling you which contact does what are wrong, so I'm gonna give each contact a new name. In the picture, you can see the metal tab on the black part of the switch sticking off to the side, we're gonna call that Tab1. The tab on the bottom nearest to Tab1 will be Tab2, and the final tab is Tab3. When you flip the switch, Tab2 and Tab3 are connected electrically, so if you don't care about the LED coming on, wiring it in is as easy as taking the two wires that went to the existing switch, and connecting them to Tab2 and Tab3. Having the LED light up when you flick the switch will be cooler, but also more complicated. If the switch is smallish or kinda plasticly, or just doesn't really feel heavy duty, then it's probably a logic switch that goes to a microcontroller and doesn't have a large amount of current flowing through it(you could confirm this by measuring the voltage and/or current and if the numbers are low that's great). This would be ideal, because we wouldn't need to worry about the power source burning out the LED. IF this is the case, you would connect the two wires to Tab1 and Tab2(you might want to throw in a resistor for good measure), (if it doesn't work, try swapping the wires, you might have it on backwards). With this setup, the LED will come on when you flick the switch and the defroster will come on. Of course if the old switch DID have a lot of current going through it (like it would if was actually switching the device on and off) connecting it this way will burn out the LED and then you'll have to rewire it to Tab2 and Tab3 to get it to work again. You could still get the LED to come on with a high current switch, but it would need current limiting and maybe a voltage regulator and other annoying things, so lets hope it's a logic switch. :)

The light from LEDs doesn't have color?

What color is 'clear'?