Thalia weak heating water valve error

I had similar issue with my 2014 Opel Astra. Heater was weak, diagnostics said valve. Have you checked coolant level and condition? Low coolant can cause this. Any specific error codes?

Coolant level is fine, looks clean. I didn't write down the code, but it mentioned the water valve not working. Could a blocked heater core cause the same thing?

A blocked heater core can reduce heat, but the valve error code is key. My Astra had the same symptoms and error code. I took it to a shop, they found a bad valve. Get a professional opinion.

Thanks, that's helpful. Sounds like a shop visit is best. They quoted 95€ for valve replacement and labor. Appreciate the help.