BMW Repair: coolant level sending unit, coolant tank, coolant level

Question
where is the sending unit located on the radiator.
I found something near the top of my radiator, but it looks nothing like the unit i purchased.
the unit i purchased has two prongs for the wire to plug onto. the only thing i find sticking out of my radiator has three recessed prongs. am i looking at the wrong thing? the car is a 92 model 525i automatic.
thanks

Answer
Who told you it was on the radiator?
The coolent LEVEL sensor tells you if you need more coolant and is screwed into the top of the coolant tank (place where you add coolant)
This sensor only controlls the idiot light on the dash and is recorded by the ecu. It shouldn't affect any poor running or cooling problem.

-cheers