Yay Knight rider stuff... okay here goes. First, those ones on ebay are absolutely horrible. They are not even close to being screen accurate. The original scanner used in knight rider used individual halogen bulbs - for some reason this created a "trailing effect" so it wasn't really just one bulb that was being lit at a time.
Those ones on ebay probably use LED lights - and they turn on and off - so there is little to no "trailing effect". Plus, they aren't very well made.
The best scanners are the ones that are made just like the knight rider movie. they are not cheap though. Typically they will run from 300-500 dollars. I have had dealings with Mark at Mark's custom kits and they do good work. I can recommend their stuff. Here is the link
http://www.markscustomkits.com/Exterior-Products.htm One if his scanners that was broken went on ebay for over $300 a few weeks ago.
The officially licensed stuff - from Louisell - well, you can't go wrong with that company because they're the only ones that are licensed from universal to make replicas. They must be super busy, however, due to the new series.
One or two companies have high quality scanners that don't use bulbs but high powered led lights - however, I have no experience with these- or the companies so I"ll leave that out for now.
If you don't feel like spending so much money then there's always the LED tube option. A lot of companies make LED tubes that can scan back and forth - some of the newer ones are better than others - I suggest you take a look at the "ICE LED scanner" (Just google it) it changes color - and you can make it do different patterns - so it'll not only match the back and forth scanner like the 80's KITT but the new version of KITT's scanner that is coming out. Plus it changes color as well. Of course, keep in mind that the LED ICE scanners are obviously thinner than the real knight rider scanner so it won't look completely accurate. However, if you're putting it behind your grill anyway- then very few people will be able to tell the difference.
Hooking up the scanner is fairly easy. There are only two main wires. You can connect them directly to your battery (red = power + and black =ground -)
So first you connect the wires to the battery - then you run the wires inside to an area near your gas pedals and connect it to the control box- and then, from the control box, you run the wires back out to the scanner.
The only really difficult part is to find a hole behind your dashboard, around your gas pedals or underneath your dashboard...(around that area) to run the wire through. Some cars have places that have existing wires for you to run the wires through - others cars require you to drill a hole.
On a side note - yes, some states say that it is illegal to drive with the scanner on - because the red flashing light on the front of the car is used to represent official business only - like the police or ambulences so be aware that someone may stop you for that. (and yes, there are reports of people being stopped)(and no, I know a lot of people have "neon underbody lights" but because those are facing downwards the police generally do not mind - or are too lazy to stop you.)
If you need further help... let me know..
and if you're a knight rider fan.. check out my new computer that I built.
http://www.youtube.com/watch?v=zNRZgVxr6fc
Thanks!!