| HI
They're actually ultrasonic doppler sensors (1 transmit, 1 receive).
I have them in my car! They're part of the Mercedes OEM Alarm system.
They're working exactly as intended, from your description. They are however disabled when the top is down. (they won't work reliably in open air!).
With the hood up, or hardtop on, the alarm should sound when triggered by these units. (shown by the LED coming on!)
just my 2 cents worth!
IAN |