There is a sensor/switch located near the front drivers side of my '02 C320. It has a metal tube attached as well as an electrical connector. It is about the size of a small aspirin bottle. I noticed it makes an audible tick, tick, tick noise similar to a high voltage electrical arcing sound. It will do this for a minute or two, then stop, then start again. The ticking is relatively fast. About 2-3 times per second. Also, you can "feel" the tick if you touch the unit.
Can someone tell me what this is and should it be doing this?