temp going down quickly

[wainie]

hi folks
hopefully not a big issue but my temp guage sits right at the bottom when driving, no matter what speed i'm going, last summer i had a new hcv and thermostat fitted to solve the 'usual' overheating problem.
since the new stat has been done my temp guage always sat halfway when idle and even at speed....it never moved!
i noticed it yesterday whilst i was the motorway, it was sat at the bottom, but when i stopped in traffic it went back to halfway and when i set off again it dropped right back down? :?

 

[warrenpenalver]

This assumes your guage is reading accurately.

The sensor may be going out of range a bit.

It is perfectly normal for temp to drop a lot when at motorway speed. The engine although under load has loads of cooling air. Then as soon as you stop it has no cooling air so the temp rockets until the thermostat opens and/or fans kick in.