1998 Audi A3 1.8T coolant light

[revo_20vt]

With the cold weather drawing in, when starting my car 1st time in the morning my red coolant light beeps up on the display. I have checked the coolant level and all is fine. This only happens on cold mornings, any advise please :1zhelp:

[kite]

Give the 2 metal prongs in the expansion tank a scrape.
Crud can build up on them to give the low warning on cold mornings.