Seat Mii Temperature Gauge Problems

I also have a Seat Mii and I experienced something similar last year. The engine took forever to warm up, and the check engine light kept popping on. The temperature readings were all over the place too. I remember reading something about the cooling grille being restricted. Have you checked the fuse box? There's a fuse specifically for the cooling system's thermal management. It might be worth a look before taking it to a mechanic.

Thanks for the quick response! I'm not very good with cars, I must admit. Where exactly is the fuse box located, and do you know which fuse is for the cooling grille? Any advice on how to check it? I really don't want to make things worse.

The fuse box is usually located either under the steering wheel or in the engine compartment. There should be a diagram on the fuse box cover that identifies each fuse. Look for something related to the 'cooling system', 'thermal management' or even 'engine cooling'. If the fuse is blown (broken wire inside), that's likely the problem. However, given the symptoms, it might be best to take it to a workshop to have it properly diagnosed. They'll be able to check the entire cooling system and pinpoint the exact cause.

Took it to the workshop as you suggested. It was a defective fuse related to the cooling grille. They replaced it, and the total cost was 52€. Thanks so much for your help, really appreciate it!