Megane temperature gauge and slow warm up

Interesting symptoms! A restricted cooling grille could be contributing. Incorrect temperature readings, a check engine light, and slow warm-up times often point to cooling system malfunctions. Have you checked the coolant level recently? Any sign of leaks around the radiator or hoses? Does the engine ever overheat, or does it just take a long time to warm up?

Coolant level is okay, no visible leaks. The engine doesn't actually overheat, it just takes a long time to reach operating temperature, especially on colder days. But would a fuse really cause all this?

A defective fuse could be the culprit if it's related to the active grille shutter system – assuming your Megane has one. If the fuse is blown, the grille might be stuck closed, restricting airflow and causing the symptoms you're seeing. Given the combination of issues, it might be wise to have a workshop perform a diagnostic scan. It could be a sensor issue, a thermostat problem, or something else entirely. But if it turns out to be a fuse, it's a cheap fix. Estimate around 52€

I took your advice and brought it to the shop. Turns out, you were spot on – it was indeed a fuse related to the active grille shutter! Replaced it, and everything's back to normal. Appreciate the help!