92 300SD I need to test the sender unit, but don't know the location of it, also is this is the same as temp sensor as well. Sorry for my ignorance. But I have some heating issues and I think I will start trouble shooting this weekend for the problem, but I'm collecting much information as possible. Please advise. By the way, car has gone 120 but no boiling or over spill. That's why I need to test the sender and sensor (if different)

If it is the same as a 300sdl it id along the firewall, driver's side at the base of the oil filter.
but i have seen some diagrams online showing the same part number in another location (forget where) for other models - good place to start looking though.