It came with instructions, you can access a pdf version on their website. It was very easy, all the wires that need to be accessed are behind the drivers knee bolster.

Just do a search on ebay for raintracker. There are three listed right now but all are listed at $79.00.

There are three models; RT-50, the original one which controls the wiper from intermediate thru high speed; the RT-50A, same as the RT-50 but with auto headlamp control and the RT-40A which controls intermediate thru low speed only. I have the RT-50 and it works very well. The new RT-50A is stated as having even better rain sensing optics then mine. There is a on-off switch that l mounted under the dash and I just leave it on most of the time. I may wire it so that it works like the Mercedes that have factory rain sensors so that it only works when the wiper switch is in the intermediate position for a more factory feel. Doing that would have taken to long when I was installing it as I was in a rush to leave for vacation and wanted it installed for the trip. It rained on me for a good 400 miles and the system worked great. My best friend drove my car and it stared raining, before he could ask how to turn on the wiper, the sensor activated the wiper. He thought that was the coolest thing he had ever seen. LOL

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'94 E320 with 272,000 miles. '92 500SEL 133,000 miles.
Mods to the '94: TomTom GPS in place of ash tray, Auto Dimming Mirror ,Memory seat, DEI 545T Auto lamps, DEI 530T Auto Up/Down Windows, DEI Remote Start, Motorola Bluetooth® Car Kit, Built in phone charger using factory phone wiring, RainTracker Rain sensing wiper, Keyless Entry, Ambient lighting of center storage compartment. Soon: factory heated seats, REST
Mercedes-Benz is my addiction of choice.
http://www.youtube.com/vanwiek