new temp sensor on my 200tdi

Heys guys hope all are well.... Ive got a 1986 defender with a 200tdi engineconversion. Orginaly the temp sensor gauge use to sit just under the red and i understand that this is because the sender in the 200tdi engine doesnt match the gauge in the car but that is where the gauge sits in this circumstance at normal engine tem. i have now fitted a new after market gauge and sender and now it says that my engine temp only reaches about 60degrees. Now i need to know is the new sonsor out or is my engine runnin too cool? Hiwcan i tell if the engine is runnin at the right temp?

Mamy thanks chris

You can get a rough idea by finding out what temp your thermostat opens at and checking the gauge

Daz