engine temp gauge low???

My polo 1.4 tdi is currently running with the engine temp gauge below a quarter (below 70C). It's only started doing it as it used to run with the gauge at halfway (90C). Shes just done over 90,000 miles on the clock.

I want to say a sensor is on its way out but I have no idea.

First diesel I've had

Does anyone know what's wrong and how to fix??

Could be the thermostat has failed in the open position. If you let it idle for a while will the temp get up to 90 before the fan kicks in?

I've left it on idle and it won't even get above fifty. Is it a big job replacing a thermostat. I'm guessing/hoping it isnt.

Quick and simple mate buy a VW one not a cheap after market one

Nothing overly difficult. If you've got a Haynes manual it will tell you everything in there. Just remember to make sure the engine is cold before you start and make sure to refill the cooling system with a 50/50 mix of water and antifreeze

Well i have finally changed the thermostat. but she still isnt warming up to 90C or even above the 50C mark.

im thinking it must be the water coolant temp gauge, any ideas??

If so does anyone know where it is located on the engine?? cant seem to find it and the haynes only tells you on the petrol engine :S

Any help would be great