Hello! With a vehicle (not mine), the coolant temperature indicator, as far as I know, has 6 LEDs. If the engine is in a warm state, normally constant 3 LEDs light up. For some time, probably at lower outside temperatures dropped off and the display from three to two LEDs. At some point, it rose again to three LEDs. I therefore suspected a defective thermostat. Now, among other things, the cooler came new, new thermostat and new coolant temperature sensor. The new thermostat is the same as the previous model and is definitely the right one – the cooling system has been properly ventilated – No oil in the cooling water and no cooling water in the oil, no smear on the oil cover – No heat loss on the oil cover – No heat loss, no heat loss, no heat loss, no heat loss. rising bubbles in the cooling water with open balancing tank and running engine – heating gets warm – no errors in the fault memory – fluctuating cooling water temperature is also visible when reading the data with a diagnostic plug during the ride Do you have a guess what the cause might be? Is it just the outside temperatures? Simply ignore? It is by the way a Citroen C3 from 2003 with a 1.4l machine (TU3JP).Thank you for your assessments.