jaguar 23kw wall hung combination boiler?

Hi I had an engineer out to look at my boiler a few month ago because the system had shut down, the engineer said it had overheated and knocked itself of, he said he had welded someting and it seemed to be working again but may need a new control panel, since this has happened the radiators dont heat up like they used to,they used to get hot now they are barely warm, any ideas on what I should do
Thanks