Temperature gauge issue

[Kokomo]

Hi all, I have a 2018 A4 Avant 1.4 petrol, my digital temperature gauge reaches operating temperature within 5 minutes (4 bars on the screen) within 2 minutes it then drops to 1 bar then works its way back up to 4 over about 20 minutes, anyone know what the problem is? Airlock? Thermostat? Many thanks 

[cliffcoggin]

Is that new behaviour or has it always been like that? Does the guage stay at the normal reading on long journeys once it has risen for the second time?

[Kokomo]

I’ve had the car 6 months, it’s always done that, after 20 minutes it reaches temperature and stays there, I noticed this morning that if I put the heater on when there’s only one bar it stays at low temperature for much longer 

[cliffcoggin]

I suspect the drop soon after starting is when the thermostat opens and allows cold water to reach the temperature sensor. Perhaps other owners can confirm if this behaviour is normal.

[Kokomo]

Yes, my thoughts too, tonight I didn’t put the heater on for about 5 minutes after I reached 4 bars (90 degrees) and it didn’t drop down at all, so probably a combination of the stat and the fan heater cooling it down, many thanks for your input, it was more curiosity than anything else as it runs fine, cheers