faulty temp sensor

Hi I’m having problems with the temperature sensor on my 04 mille r. she runs o.k for a bit but after what seems to be an ever shortening amount of time the red warning triangle comes on and temp gauge flashes an indicated 135. This continues until i switch it off then on again (via kill switch once iv’e slowed down a bit ) the reading then goes down to a much more realistic level. Iv’e contacted my local Essex dealer who will be contacting Aprilia soon regarding this matter, but having already been to them to sort out my clutch and rear brake I know they tend to be a bit cagey about pre-existing problems on their lovely Italian machinery . Any info at this stage will be gratefully accepted thanks .. Just realised my warranty his run out by 5 days BUMMER! All the best Sid.