Vaillant EcoTec Pro not reaching set temperature

Here is what I've noticed today. When I remove the front panel, it started to heat up the water continuously. I set the temperature to 50 deg but it didn't stop at 50 and continue to heat up above 60 where I had to close the tap. So obviously my NTC sensor is not working. I better purchase a new one and try again after replacing it. I'll update the post. Thanks for your helps
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You don't have an issue with the NTC based on what you've said, the display shows the primary heat exchanger temperature not the domestic hot water temperature, so it should be between 10 to 20 degrees higher on display.

The rules of this forum are quite clear with regards to DIY gas advice not being allowed, removing the case on that boiler is removing the case seal, and the fact that it runs fine with case off give me serious cause for concern about there being a potential combustion issue on that boiler, so my only further advice would be to refit the casing and get a competent engineer in to repair and test it, you've proven enough to know that its not a simple setting or DIY issue that can be fixed without the correct tools and knowledge to keep you safe.

Good luck

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