If you Google the word, you will get a definition in wikipedia. It's a lot faster than typing the question and then waiting for an answer.
"COOLANT THERMOSTAT" -COOLANT TEMP BELOW THERMOSTAT TEMPERATURE
There is supposed to be an engine thermostat . Do you mean that someone has removed the engine thermostat ? What year of Ford Ranger and what year ?
A thermostat is a heat operated device designed to control temperature or provide a safety cut-off
Thermostat
if you mean the gasket between the thermostat housing and the hose connection bell yes you do but you should use a thermostat to keep the engine at constant operating temperature for which it was designed it will run more efficiently and last longer
Depends on what you mean. If you mean "What happens when I change the thermostat setting", then the answer is that the room (or house, or apartment) gets warmer or cooler. But if you mean "What happens when I change from a mechanical to an electronic thermostat" then the answer is that it is less sensitive to position and orientation, and it may also be programmable, operated from a remote control, or even operated over the Internet.
If, by "thermostat" you mean the radiator flow valve that controls engine coolant temperature, yes. All liquid cooled engines need such a thermostat.
Assuming you mean a 2001 Taurus, original equipment would be a 195 degree F thermostat.
P0128 is thermostat malfunction. The thermostat needs replaced.
Trouble code P0128 means:Coolant thermostat (coolant temp below thermostat regulating temp)
Trouble code P0128 means:Coolant thermostat (coolant temp below thermostat regulating temp)
You may mean "bimaterial" strip which is a part of a thermostat.