My engine coolant temperature has always consistently been at ~ 90C/194 F, but recently its been erratic, now consistently low at 60-70 C. (140-160F) The orange EML light has come on a few times with error P0128 : Coolant temperature below thermostat regulating temperature.
Does anyone know what the normal coolant temp is. I have a 2017 C200 petrol (UK) W205. Is 60-70 Centigrade OK, or should I be worried about this? Should I leave it or maybe change the thermostat and/or maybe the coolant temperature sensor. Thanks

Mine goes up to 90°C and stays there. C200 AMG line. I was wondering why yours went down to 60-70. Is it that cold in the UK these days. Something wrong with the car. It should remain at 90.

Thanks for your comment on this. It's not especially cold here at the moment, and actually this problem started a few months ago in the warmer weather. It was intermittent for a while. Now its always somewhere 60-70C rather than 90 C as before. I'm thinking the thermostat might be malfunctioning. Stuck open. Any advice from anyone on what other possibilities would be appreciated.

Is the fan kicking at all?

The fan doesn't kick in if I leave the car idling with the hood/bonnet open. Not sure when I'm driving. How do you know if the fan comes on when driving?

My fan kicks at 90 degree. So normal temperature is 80 to 90 yours is at 70. I dont think its a major issue.