A2 temperature indicator

[Alf_redo]

HI,
I have a 2001 1.4 A2 petrol. In the last year I have noticed some erratic behaviour of the engine temperature indicator.

Normally temp indicator is rock solid in 12 o'clock position once engine has warmed up. When things started to go wrong the gauge slowly drifed back to minimum temperature whilst driving along.

Now most of the time it hardly ever gets off the starting blocks. Strangely, if I whack on the heater to max, the temperature gauge will come alive and head toward the normal temperature reading. Once I can stand the tropical temperatures no more & turn off the blower, the temperature gauge will go to sleep again.

Any ideas or anything similar seen by anyone else?
Alf_redo