Vaillant eco tec plus 837 continuously 'loading'...

29 Oct 2021
Reaction score
United Kingdom
Any heating engineers able to help?
Apologies if previously covered. I did try and search.
Just arrived back from holiday and our boiler won't start up. The screen won't power up and is just continuously flashing 'loading'.
It doesn't get as far as showing any error codes. It sounds like it's repeatedly about to fire up for a split second but then cuts out.
... so no hot water or central heating.
Green flashing light on the front under the button with the circular arrows on.
Hope that makes sense!
Any ideas?
Thanks in advance.
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+2 for pcb, don’t think I’ve known it to be anything else.

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