I am baffled

Driving round town and temp is rock steady normal.

Onto motorway and temp drops to zero. For next 100 miles gauge moves between zero and 1/4 but never higher. Most of the time hovers a couple of notches above zero.

Back into town gauge returns straight back to normal and does not move.

It did exactly the same thing on the outward and return journeys, which were a day apart.

Anyone any ideas.

Thanks, Paul.

 

Thermostat stuck open??