Thermostat -200tdi

i've got a 200tdi, h reg discovery 1, 1991, thas done 210000 miles. what i have noticed recently, and what i belive has happened since buying the vehicle 6months ago, that on start up and the engine ticking over, the thermostat (the thermostatin engine temperature gauge) inthe dashboard housing immediatly goes from being cold to going to the first line on the gauge segemnt marker even before the engine has even warmed up. this happens either when the car has been left for a few days to afew hours(when you possibly would expect it). any remedy on what this might entail? as in dodgy thermostat or something more serious?

thanks

this would probably be nothing to do with the actual thermostat its self but the temperature guage and measurement.

the actual thermostat is in the top front of the engine and is about as round as a 1/2 pint glass. on the side of the housing there is a probe to measure the temperature for the dash, this has a connection on it heading back to the dash. if you want to check the function of the dial then simply unplug the cable from the probe and short it on the engine and you shoud see the level go all the way to the top.

By the sounds of thing you may have a small isue with the probe its self.

aye the sensor unit is the most likely suspect. gauges very rarely go wrong.