Megane Temperature Sensor Error

I had a similar issue with my Megane. The air conditioning control unit was the problem. Have you checked the engine cooling system? A defective temperature sensor can cause these symptoms.

Engine cooling system? How do I check that, exactly? Is that something I can do myself, or am I looking at a trip to the shop? Could it be related to the HVAC system or does the temperature sensor need some kind of calibration?

Checking the system's sensors and wiring is a start, but without diagnostic tools, further analysis will prove difficult. The defective air conditioning control unit may very well be the cause as problems in the engine cooling system trigger the described symptoms and the air con's failure to function, which would amount to roughly 980€ at a certified workshop. I recommend you seek professional assistance.

Thanks! Took it to the workshop, and you were spot on – the air conditioning control unit was indeed defective. All fixed now!